HDR: an introduction to high dynamic range photography 9780596510176, 0596510179

Table of contents :
Common Terms and Definitions......Page 5
Debunking Myths About HDR......Page 6
Making the Best Source Images......Page 8
Keeping the camera steady between exposures......Page 9
Image Capture Bracketing Methods......Page 11
Basic Auto Exposure Bracketing workflow......Page 12
If your camera does not have Auto Exposure Bracketing......Page 13
Take Total Control with a massive manual bracketing series of source images......Page 14
File and Folder Organization......Page 15
Ready, Set…Before You Go......Page 18
HDR Generation in Photomatix Pro......Page 19
Tonemapping the HDR for output: Details Enhancer Method......Page 22
Tonemapping with Tone Compressor......Page 24
Batch Processing with Photomatix Pro......Page 26
Single File Tonemapping......Page 27
HDR Generation with Adobe Photoshop CS2......Page 28
HDR Conversion in Adobe Photoshop CS2......Page 36
FDRTools Advanced Workflow......Page 39
HDR Generation in FDRTools Advanced 1.8.2......Page 40
HDR Processing with FDRTools Advanced......Page 44
Saving the HDR and LDR output image in FDRTools Advanced......Page 47
Software Comparison: Which HDR Processor is right for you?......Page 49
Final Image Adjustments of your HDR Output Image......Page 52
Final Thoughts......Page 57

Citation preview

HDR: An Introduction to High Dynamic Range Photography

Contents

By Jack Howard

Final Thoughts .........................................57

Copyright © 2007 O’Reilly Media, Inc. ISBN: 978-0-596-51017-6 Release Date: February 28, 2007

A step-by-step introduction to one of the hottest new imaging trends. We’ll walk you through making the best HDR images—from image capture to digital darkroom tips and tricks.

Debunking Myths About HDR .................6 Making the Best Source Images ...............8 Image Capture Bracketing Methods......11 File and Folder Organization .................15 Ready, set…before you go.......................18 Photomatix Pro workflow .......................19 Adobe Photoshop CS2 Workflow...........28 FDRTools Advanced Workflow .............39 Software Comparison: Which HDR Processor is right for you? ......................49 Final Image Adjustments of your HDR Output Image ...........................................52

Jack Howard is Associate Online Editor of PopPhoto.com/PopularPhotography & Imaging where he tests and reviews cameras, lenses, software, and other camera gadgets. He is also an established freelance photojournalist whose work has appeared in The New York Times, The Asbury Park Press, The Star-Ledger and many other newspapers. He lives in New Jersey with his wife Corey and their German Shepherd Dog, Bailey.

Find more at shortcuts.oreilly.com

An Introduction to HDR High Dynamic Range (HDR) imaging is one of the hottest new digital imaging trends. As of January 2007, there are over 100,000 images tagged "HDR" on the Flickr photo sharing web site alone. The HDR process involves combining several selectively exposed photographs of the same scene and merging them into a single image, providing a much greater tonal range than is possible with traditional low dynamic range images like those produced by today's digital cameras in a single shot. By exposing different images for the shadow, midtone, and highlight elements in a scene, it is possible to create one image that overcomes the 5-7 stop exposure value limits of most current digital cameras (5-7 stops is the effective dynamic range in a single digital camera image, although the sensors do have a total range of about 12-14 stops.) You no longer have to lose shadow or highlight detail in scenes with dramatic differences between the darkest and brightest elements. By bracketing a series of images— shooting a number of photos in rapid succession at different shutter speeds—and running them through an HDR processor, you will create an image that has great detail gleaned from the tonal range of the all the source images. This photomerged image can then be printed or shared online. This twilight beach scene was created by combining eight images over about 10 exposure values. It was processed in Photomatix and had minor post-processing fixes in Adobe Photoshop CS2.

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Why try HDR imaging? Imagine you're visiting a cathedral with great stained glass windows, but there is low available light inside the building to show the ornate interior designs. There is also a sign stating “No Flash Photography.” Checking your meter, you see that there is a seven stop difference between the brightest highlight area and the deepest shadow detail. With traditional imaging, you are forced to choose and expose for the stained glass windows—turning all the interior to muddy shadows with little or no detail—or you can expose for the interior details, but overexposing the stained glass, which eliminates most of their detail and color. The final option is to pick a middle-range exposure and attempt to twist the single flat image into something that resembles your impression of the scene.

With single-shot photography, it would be impossible to capture the interior shaded details, the blue sky, and the sunburst in a single frame. With 4 images bracketed at 2 stop increments, Adobe Photoshop CS2 was able to combine and process this HDR image. Saturation was boosted during post-production in Photoshop CS2 to emphasize the complementary colors in the image.

There are ways to capture more exposure value detail in a single image: graduated density filters, fill-flash, reflectors, and capturing a single “compromise image” that is exposed for the middle values, with the intent of post-production dodging and burning. However, HDR imaging makes it easier to capture detailed scenes such as this cathedral scenario when it's not possible or practical to squeeze every detail of exposure into a single frame.

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By capturing a bracketed series of photographs matched to the exposure extremes of the scene, HDR makes it possible to create an image that overcomes the dynamic range limitations of current camera technology. HDR imaging involves multiple steps and multiple processes, from low dynamic range bracketed image capture to post-HDR processing in your regular image editing software, such as Adobe Photoshop CS2 or Photoshop Elements. It can be confusing at first, but with a little practice, it makes perfect sense. Just make a few small adjustments while shooting, follow the HDR processing tutorials, and you’ll be on the right track to jump right in to HDR imaging. This image was merged from five source images bracketed in 1-1/2 stop increments to capture details in the buildings and the sky. It was processed in Photomatix, with minor postprocessing fixes in Adobe Photoshop CS2.

This Shortcuts guide walks you through the basic steps of this process, from image capture to adding your final image quality adjustments in your regular photo editing program after making your High Dynamic Range image. We'll clear up some HDR imaging myths, and offer advice on how to make the best HDR images with DSLRs and compact digital cameras. Along the way, we will look at three HDR imaging programs: Photomatix Pro, Adobe Photoshop CS2, and FDRTools Advanced. (Each of these programs is available for both Windows and Macintosh computers.) We examine the basic workflow for HDR capture and file management, and then examine each program's strengths and weaknesses. This eBook provides the HDR beginner with a great foundation for jumping right into this cool new imaging process.

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Common Terms and Definitions One of the most confusing things about HDR imaging is the various usages of terms such as HDR Source Image, LDR Source Image series, HDR Output Image and so on. There are input files, output files, HDR, LDR, camera RAW and so on. We will try to be internally consistent and strive for clarity in our explanations and descriptions, although terms and usages vary from program to program. Here are a few terms you will encounter in this guide. High Dynamic Range (HDR) Refers to 32-bit images and the vast tonal range of this 32-bit color space. Low Dynamic Range (LDR) Refers to 8- and 16-bit images with a smaller area of tonal range and of these color spaces. HDR Image, HDR Source Image, 32-bit image A 32-bit image, usually photomerged from several LDR images via an HDR Generator. Used generically to refer to various 32-bit file types such as Radiance (.hdr) and OpenEXR (.exr). LDR image, LDR image series, LDR source image series Refers to a single 8- or 16-bit image, or Camera RAW image, or a series of such images that are exposed differently to increase tonality when photomerged to generate an HDR Image. HDR Output Image, LDR Output Image An 8- or 16-bit image that is the result of tonemapping a 32-bit image information via algorithms to bring the expanded 32-bit tonal range into a color space that can be displayed and printed on conventional monitors and printers. Tonemapping, Tonemapped The processing of a 32-bit HDR image so that the expanded-bit tonal range and color space can be displayed and printed on conventional monitors and printers that support 8- and 16-bit color space. Photomerging, Photomerged The process, or processed, result of combining several differently exposed LDR images of an identical scene to create a single 32-bit image. An HDR source image. Bracketing, Automatic Exposure Bracketing, Manual Bracketing In-camera techniques that change the shutter speed to capture a given scene at different exposure values, resulting in a series of LDR images with different exposure values.

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Exposure Value Equivalent to stops in camera metering. Here it is used in the relative, not absolute context. EV -1 refers to one stop below a normal exposure for a given scene, not to the absolute value scale. Camera RAW A generic term that encompasses the various proprietary Camera RAW formats. Much more concise than listing CRW, CR2, NEF, PEF, ORF, and so on each time Camera RAW is mentioned.

Debunking Myths About HDR If you search the web for information on HDR photography, you’re likely to come across a number rules and declarations about HDR photography. Some are true, but many of these online statements are false. You must shoot RAW for HDR generation. NOT TRUE. Depending on the program, the LDR source images may be in several file formats including Camera RAW, JPEG, TIFF, or PSD, among others. Shooting RAW offers a bigger starting color space and dynamic range in the source images, but it is not true that RAW capture is a necessity. Likewise, 16-bit files are not a necessity either. Every image in this book began its life as a series of 8-bit JPEGs. Your camera must have Auto Exposure Bracketing (AEB) to capture source images. NOT TRUE. Most DLSRs have AEB, and there are some good reasons to use AEB for source image capture, but it is not a necessity. Manual bracketing, by either changing shutter speed, or by using Exposure Compensation settings (+/- or EV on most cameras) can also create bracketed source images. Shooting burst capture in AEB mode on a tripod ensures that there will be minimal camera or subject movement between source shots, but AEB is not a must-have requirement. A DSLR is necessary for HDR Imaging. NOT TRUE. Most current compact digital cameras have features that allow for HDR imaging—such as exposure compensation—and many current compact cameras have manual or semi-manual exposure modes. HDR images always look artificial and overworked. NOT TRUE. Depending on the source image series, and the HDR processing settings, the results of HDR processing can range from photorealistic to fantastical. HDR processing will make a boring scene more interesting. NOT TRUE. It will simply increase the relative dynamic range of the image and provide more tonal detail to a boring scene. There is one HDR program that is far and away better than the rest. NOT TRUE. Each program we will explore has its own strengths and weaknesses, but

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each program can produce stunning results ranging from subtle to surreal, depending on the skill of the photographer, both with image capture and image processing. There is a specific formula that will work for processing every HDR image. NOT TRUE Based on my experimentations and understanding of the “crazy math” behind HDR processing, there is no one setting that will work for every HDR image, every time. Due to the local operators algorithms, the settings that produce good results really are image-specific. After a while, some baselines may present themselves to your shooting style, but there isn't a specific set of magic numbers to plug into the HDR processors that will ensure high quality results every time. True 32-bits per channel HDR images cannot be displayed properly on today’s monitors, nor printed on today’s photo printers. TRUE. There are several 32-bit per channel file formats, and none can be displayed or printed in all their 32-bit glory, so it is necessary to crunch these 32-bit files back down into “normal 8- and 16-bit” space. OK, so on that last point, doesn’t that make HDR imaging a scam? NOT TRUE. When the 32-bit file is crunched back down to normal bit space, the HDR processing engines bring along an interpretation of all that extra color and tonal range information, which produces a viewable, printable 8- or 16-bit file that has tons of the detail information of 32-bit true HDR image. HDR Imaging is not “real photography.” NOT TRUE. HDR imaging is simply a method to compensate for the limitations of today’s sensor technology, to expand the amount of information of different exposure values in a given scene. It is true that it is a multiple source image process, but there is a long legacy of combining source images in both film and digital capture in the history of photography to overcome limitations of equipment, and to expand the boundaries of photographic creativity. HDR processing is a complete workflow, and HDR processing is the last step of a digital workflow. NOT TRUE. HDR processing is actually the first step in digital image optimization. Once the 8- or 16-bit image is produced by the HDR processor, it should be brought into your normal image editing program for final global and local image quality corrections, such as contrast adjustment, resizing, color balancing, and print output optimization. For web display, 8-bit should suffice, but for printing, 16-bit will produce better results. HDR Imaging will make any scene look better. NOT TRUE. Despite some advances in “ghost removal,” still scenes without moving elements work best for HDR images. Also, since HDR processing can equalize shadow, midtone, and highlight detail (which reduces overall tonal contrast), images with color and texture contrast elements tend to work better than uniformly colored and textured High Dynamic Range-Photography

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images. Additionally, HDR imaging really shines when there is a dramatic difference in exposure values in the image elements. If there is mostly uniform lighting without a dramatic difference in EV between highlights and shadows, HDR processing may not be necessary for that scene. HDR imaging is difficult and should only be attempted by experts. ABSOLUTELY NOT TRUE! It is a multi-step process, and a bit of logical file management is necessary, but the beauty of HDR imaging is that it is, in many ways, easier than ‘“normal” photomerging, which involves masking, dodging, burning, and blending multiple layers to combine differently exposed source images. HDR Imaging is addictive. VERY TRUE! Once you get the feel for HDR imaging, you’ll see the world and all the potential for using HDR image capture and processing techniques to add a new element to your photographic vision.

Making the Best Source Images A great final HDR image begins with the successful image capture of a photographically interesting scene that challenges modern camera sensor technology. The power of HDR imaging is that it can overcome the dynamic range limitations of digital cameras to capture tonal detail across a much greater exposure range by taking a series of differently exposed frames of the same scene. If you've ever shot an interior scene with glowing white blown-out windows, but wished to capture the world outside that room as well, HDR imaging can help. If you've ever had to choose between capturing detail in a backlit skyscraper and completely losing the sky, or conversely, been forced to silhouette the skyscraper to show the dramatic clouds in the sky, HDR imaging can help. The real strength of HDR imaging is the ability to overcome these low dynamic range limitations. In scenes without extreme exposure differences between shadows and highlights, HDR imaging may not be necessary. But if you find yourself in a shooting situation where it is simply not possible to capture good image detail throughout the entire tonal range in one image, HDR imaging can make it possible.

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This symbol means Automatic Exposure Bracketing on almost every modern button-based camera. In menus, it is usually abbreviated as AEB.

Because HDR imaging involves multiple captures of the same scene, still images with no moving elements work best. Even the slightest movement of a flag flapping in the wind, a car moving down the road, or a pedestrian crossing the street will appear “ghosted” in the final image. Strive for perfectly still compositions with virtually no moving elements to get started. Because HDR imaging involves multiple exposures of the same scene, some specialized shooting techniques are needed to yield the best low dynamic range source images. First and foremost is a solid shooting platform which will keep your bracketed source images aligned and in registration during the photomerging process.

-2, 0, and +2 Histograms.

Keeping the camera steady between exposures Shooting from a stabilized platform to ensure image alignment helps to make the best HDR images. The obvious choice for ensuring image alignment is a sturdy tripod. A sturdy tripod ensures that all the images are aligned exactly pixel to pixel during the merging process. High Dynamic Range-Photography

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If it's not possible to use a tripod, consider a monopod, and shoot your series in rapid succession, that is, in a single burst (if your camera permits this operation). Even if there is slight movement between the shots, most of the HDR generation programs offer an image alignment utility. In many situations where full-sized tripods are not permitted or practical, such as museums and cathedrals, consider a tabletop tripod, a beanpod, gorillapod, or a Manfrotto super clamp to make a stable shooting platform. These small, unobtrusive stabilizers come in handy and don't take up much space in a camera bag. If it's not possible to use any camera stabilization method, hold your breath! Hold the camera steady as you shoot your series in rapid fire burst mode, and hope that the HDR generation program will succeed with image alignment (it's not guaranteed, but it’s worth a shot). A remote trigger or cable release combined with a tripod will also minimize camera movement between captures. Cabled or wireless remote triggers are available for most current DSLRs and some compact digital cameras. Check your camera's user manual or the camera manufacturer's website for availability. For perfectly still shooting opportunities, such as interiors or still life shots, consider using the camera's self-timer and mirror lock-up combined with a remote trigger and a sturdy tripod. This is perhaps the “best of the best” practice, but it is practical only when there is no chance of any subject movement: such as in still life and completely controlled interiors. For scenes with the potential for even slight movement during source image capture, the self-timer method is not recommended. Even with a wide angle lens, clouds on a still day may move slightly between frames when there are several seconds between each exposure.

Ghosting: Moving image elements can cause problems when source images are combined.

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Image Capture Bracketing Methods Image capture for HDR imaging is slightly different than traditional single-shot low dynamic range photography. The goal is not necessarily to capture a single frame that best represents the scene before the camera, but to capture a series of different exposures that are intended to best capture the various tonalities contained within the scene. In simpler terms: HDR imaging begins with a bracketed series of low dynamic range images that run the gamut from underexposure to overexposure. Perhaps counterintuitively, the underexposed source images from the series are used for the extreme highlight details, and the overexposed source images provide the shadow detail. It makes perfect sense when you think about it for a moment. In the underexposed images, all but the spotlights, sun disk, or other extremely bright image elements will be thrown to shadows, but the highlight areas will have a degree of detail. In the overexposed images, all but the darkest shadows will be blown out and whiteclipped. But those very dark shadows and low tones will appear close to normally exposed—providing shadow detail that would be lost in a normally exposed tonal range. By combining these extremely exposed source images, along with like images from the series that are exposed for the middle tonal areas, the tonal information gleaned from all photos provides the HDR generation program with enough information throughout the image curve to create an HDR output image that shows the expanded detail throughout the tonal range. This output is also in a bit space that can be displayed and printed. How does one create the variously exposed source images? Depending on the specific camera, there are several methods for creating a bracketed series. Regardless of the bracketing method, the only exposure variable that should be adjusted is shutter speed. Changing ISOs may introduce noise pattern issues during HDR generation. Changing the aperture will also affect the depth of field, which will also cause image quality problems during HDR generation and processing. Change exposure only by changing shutter speed. Flash should not be used for basic LDR source image capture, because the strobe will attempt to expose all the images properly. Additionally, if possible, disengage autofocus from the shutter button, either via your camera’s custom functions, or by using manual focusing mode. Even a slight focus shift between exposures will have a negative impact on the photomerged series.

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Depending on the specific camera model, AEB should be an option in almost all shooting modes—Full Program, Aperture Priority, Shutter Priority, and Full Manual. To ensure aligned images with identical depth of field between exposures, it is best to use either Aperture Priority or Full Manual modes for LDR source image capture. If neither of these is an option, use normal Program mode. It also makes sense to use a low ISO to minimize digital noise in the source images because the subject matter is still.

Auto Exposure Bracketing The simplest and easiest method is Auto Exposure Bracketing (AEB), which is a feature found on virtually every DSLR along with many compact digital cameras. Check your camera’s user manual for brand- and model-specific instructions on how to set exposure bracketing. AEB will shoot, at minimum, three photographs at a set exposure value offset (+/2/3, +/- 3, +/- 1.7) in either 1/3 (or .3), ½ (or .5) or 1 (1) stop increments. For simplicity’s sake, we will use only fractional values throughout this eBook, but the concepts and techniques and exposure offset are identical even if your camera using decimal notation. (Note that in weird camera math “1/3” equals “.3” and “2/3” equals “.7”, not “.666….”) Also note that certain cameras work in 1/3 EV increments, others in 1/2 stops, and some high-end cameras offer the option of choosing 1/3 or 1/2 increments. The 1/5 stop differential between 1/2 and 2/3 is negligible, so don’t fret about the numbers given in the following descriptions if your camera does not match these exactly.

Basic Auto Exposure Bracketing workflow Check your owner’s manual for model-specific instructions on how to activate AEB: • Activate AEB, and select a number of images in the series (3, 5, 7, etc., depending on camera model). • Select an exposure value offset, 1/3, 2/3, 1, 1 1/3, etc. The greater this number, the greater the exposure difference between each captured frame. • Set your camera to “Burst” mode to capture the AEB series with one touch of the shutter button (optional.) • Check exposures and histograms in playback mode to ensure that the AEB series has enough variation in exposure range between the underexposed and overexposed shots. The “middle” (0 Exposure Compensation) photo should look very much like a normal exposure. For most scenes, this “normal” exposure histogram should follow a bell curve, with the peak near center.

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• If there is not a significant variation in the exposure of the AEB images, increase the Exposure Value offset. Repeat above steps. That’s the basic AEB workflow. Nice and simple. But, there are a few ways to expand AEB to create more LDR source images with your DSLR (and some compact digital cameras). Next up, advanced AEB techniques and tips.

Getting even more exposure value range with Auto Exposure Bracketing What if you want to take images that capture an exposure range that is wider than your camera’s maximum AEB setting, but aren’t quite ready to tackle manual bracketing? By combining your camera’s exposure compensation setting with AEB, you can cover more ground with two sets of AEB, shot one after the other. For example, set your camera’s Exposure Compensation setting to its maximum negative value, -2, for example, and set AEB to this same numeric value +/-2. The +2 AEB image with -2 Exposure Compensation will actually be normally exposedthat is, not have any exposure compensation applied, as the +2 and -2 will cancel each other out resulting in a normally exposed image. Now repeat this process, but set the Exposure Compensation to +2, and keep the AEB again at +/-2. Now, the -2 AEB image will be normally exposed, by the same formula as above. Presuming this is a 3 image AEB series, you’ve now captured 6 source images with an exposure range of -4, -2, 0, 0, +2, and +4. Discard one of the zero valued (normally exposed) images, and you’ve now created an LDR source image series of five images covering nine exposure values!

Create more source images by changing AEB value and repeating the AEB sequence Another way to increase the number of source images with AEB is to change the bracketing amount and reshoot an AEB series of the same scene. Set AEB to +/-2 and capture three bracketed images. Then set AEB to +/- 1-1/2 and capture three more images. Repeat at +/-1, and +/- 1/2. Discard three of the zero-valued (normally exposed) images and you’ve created an LDR source image series of nine images covering five exposure values! It’s also possible to combine the previous two techniques to make a giant set of LDR source images, bracketed across a very wide exposure range, with only a subtle exposure difference between adjacent images. You may or may not want to use, nor need to use, every LDR image in such a big series, but experimentation is a big part of the HDR experience.

If your camera does not have Auto Exposure Bracketing Don't worry, it's not the end of the world. Almost every digital camera in the market, from entry level compacts to pro-level DSLRs have an Exposure High Dynamic Range-Photography

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Compensation/EV function. Some variation on +/- usually indicates this setting, if it is a button-based function. On other models, it is a menu-based option, so check your camera’s user manual for model-specific instructions on setting Exposure Compensation. You should also note that on many models, Exposure Compensation is not a selectable option in full manual exposure mode, since it's not needed. You should be able to use either full Program or Aperture Value mode to adjust the exposure. 1. Set your camera on a tripod or tripod substitute, as described above. 2. Select either Full Program or Aperture Value Program. 3. Turn the on-board flash to “Off.” 4. Activate the camera’s Exposure Compensation function and select the maximum negative exposure offset. Capture your underexposed image. 5. Set Exposure Compensation to zero and capture your normally exposed image. 6. Set Exposure Compensation to the maximum positive value and capture your image. You have now captured a three-image series that covers a significant Exposure range by using Manual Exposure Bracketing. To create a source image series with more images, repeat above steps, but capture an image at more evenly spaced exposures throughout the camera’s Exposure Compensation range: -2, -1, 0, +1, and +2, for example.

Take Total Control with a massive manual bracketing series of source images When shooting with a DLSR and certain advanced compact digital cameras, manual exposure mode combined with manual bracketing offers total exposure control over a very large exposure value range. Using this method, it is possible to make a series of source images where all but the hottest scene elements are slightly underexposed and all but the darkest shadows are slightly overexposed, overcoming the EV range limitations of the Auto Exposure Bracketing methods described earlier. The example below will yield an exposure value range of 11 stops with 1/60 as the middle point/normal exposure. • Mount the camera on a tripod. • Set the camera to full manual mode • Select an aperture and ISO. • Compose and focus the scene through the viewfinder. High Dynamic Range-Photography

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• Turn autofocus off. • Adjust the shutter speed until the in-camera metering is showing normal zero-balanced exposure and note the shutter speed, for example, 1/60. • Increase the shutter speed (which will lead to underexposure showing on the meter and in the resulting image) by five full stops, 1/2000 in this instance, based on the 1/60 given above. • Select a bracketing interval in either 1/3, 1/2 or full stops. For simplicity's sake we will use full stops for this example. • Capture the scene at 1/2000 (-5 based on a 1/60 metering) and adjust the shutter speed to 1/1000 (-4) and recapture the scene. Repeat in full stops all the way through to five full stops over the metered exposure value: 1/500 (3), 1/250 (-2), 1/125 (-1), 1/60 (-0), 1/30 (+1), 1/15 (+2), 1/8 (+3), 1/4 (+4), 1/2 (+5). This will yield an 11 image series across eleven exposure values. Of course, it's possible to create a series of source images with more photos by shooting in 1/2, 1/3, or 2/3 stop increments across the same exposure range. Conversely, a shorter series can be captured by shooting in 2 stop increments across this same exposure range. Depending on scene-specific captured information in the bracketed series, every image in the series may not be necessary to obtain the best results once the images are ready to be photomerged. However, shooting more source files across a very broad exposure range allows for more experimentation within the HDR programs. It's better to start with too many photographs than not enough! Now that you’ve captured a series of LDR source images, it's time to transfer them to the computer and get your files organized. Organization of files and folders for source images is very important in HDR imaging. So important that it merits its own chapter.

File and Folder Organization HDR imaging involves multiple steps and multiple files for each final output image. For this reason, logical file naming and organization is a very important part of the HDR workflow. Without a logical file and folder naming strategy, it is very easy to get confused as to which images are part of what series, and where to save the final output image (or images.) HDR imaging can quickly gobble up available hard drive space, too, especially when shooting in Camera RAW format, so it’s wise to consider a large capacity High Dynamic Range-Photography

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external hard drive for photo storage. Copy the LDR source image series to your computer using your normal file transfer workflow and put the files in your normal photo storage architecture, and keep the folder window open. Let’s look at a folder I've created that includes three series of images that were created for this book. Currently, this folder is residing on the desktop. It will eventually be transferred to the HDR_Source_Images folder on my external hard drive, along with similarly named folders for HDR source images.

Nested inside the HDR_Avon_Twilight_010607 folder are three subfolders, A_Lantern_Series1, B_Lantern_Series2, and C_Fishing_Club.

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The photographs in this series contain the original in-camera file names, prefixed with the alphabetical value and the descriptive name of its folder; in this example it’s A_Lantern_OriginalFileName.jpg. The images in B_Lantern_Series2 follow the same naming logic, and are titled B_Lantern_OriginalFileName.jpg. You can guess what the files in C_Fishing_Club are titled.

It’s up to you whether to move or copy your LDR source images to a new folder outside of your normal photo archiving architecture. The HDR generation and HDR processing functions are non-destructive in relation to the source files, meaning completely new files are created during the processes, and your original images will remain unaltered. In either case, however, adding the alphabetic and subject/geographic prefix descriptors to the original file names will help to both jog your memory at a later date, and in sorting the files during the HDR generation and processing workflow. Eventually, each source image series folder will acquire new subfolders with 32-bit HDR format files, Extensible Metadata Platform sidecar file settings, and HDR output images. There's a lot of file mapping and folder navigation involved in this process. But, following a file naming strategy such as this will save time and help keep you organized when we get to actual HDR processing—which is just a few pages away!

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Ready, Set…Before You Go It may seem as if there’s a lot to do before getting started with HDR processing, but don’t worry, this section is quite short. We're going to jump right into HDR processing tutorials on the next page. There's just a couple of computer-related points to mention that didn't fit into the file organization chapter. There are several 32-bit file formats available: Floating point Tiff (.TIFF) Radiance (.hdr), and OpenEXR (.exr), among others. Floating point tiffs are huge—over 100MB for a single HDR file from a modern 8- or 10-megapixel camera. Radiance and OpenEXR use different compression algorithms and both offer a good balance between fidelity and compression, and don't take up quite as much disk space. For a seriously technical deep dive into the differences between the various file formats, check out: http://www.anyhere.com/gward/hdrenc/hdr_encodings.html For a beginner purpose, any of the three previously-named file formats will work for HDR imaging. As an added bonus, all three programs can handle these file formats. A 32-bit Radiance (.hdr) file created in Photomatix Pro can be opened and processed in Adobe Photoshop CS2 or FDRTools, and vice-versa in all directions. There is no need to regenerate a new HDR from your LDR source image series for each program. HDR imaging for still photography is still in its infancy, and the numbers and setting offered in the following examples work for the specific LDR series, but the same numbers and settings applied to a different series of images may yield wildly different results. The algorithms behind crunching the 32-bit information back down to 8- or 16-bit space really feels image-specific. Experimentation is the key to mastering HDR processing. If an output image doesn't feel right using five exposures from a series, try using four source images instead. Or three source images. Or seven. Don't get locked into a hard set of numbers for the settings. Trust your eyes and your heart as you push and pull the sliders and curve controls. When experimenting, consider using small web-sized files to speed processing and conserve disk space. And on the subject of resizing and cropping: even if you know you want to crop the composition, work with the full images, or the full images which are downsampled. Crop the output image, not the source images, to ensure alignment.

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Let your sense of aesthetics control the final image. Usually, I strive for photorealism, and tend to lean towards heavy color saturation. You may like desaturated images with a more illustrated feel—it's all part of your personal vision. In either event, the program navigation and steps are the same. For Photomatix Pro, the on-screen images will be Macintosh-based. For Adobe Photoshop CS2 and FDRTools, the on-screen images are Windows-based. The only real difference between any of these programs on either platform are cosmetic, but the commands and functions are identical. We are also working with the standalone versions of each program, not plug-ins. Now, we're actually going to begin step-by-step tutorials with these programs.

Photomatix Pro workflow Photomatix Pro 2.3 is available for download at http://www.hdrsoft.com for both Macintosh and Windows operating systems. You can try before you buy with the demo version, but it will watermark your output images. Photomatix Pro features a large preview window for tonemapping your HDR image, and all of the image adjustment settings are slider-based. Program navigation can be a bit confusing at first, but after a few times, it gets easier. Photomatix also includes some non-HDR exposure blending methods and a batch processing function, which we’ll also take a quick look at. For our step-by-step below, we are using eight images from a massive manual bracketing series, but you can start with a simple three image series if you prefer. The commands and functions are identical.

HDR Generation in Photomatix Pro Open the bracketed low dynamic range source images you wish to convert to HDR into Photomatix Pro via the File>Open command path (or by dragging into the program window in Windows, or by dragging onto the Dock icon in Mac OSX). Images may be JPEG, TIFF, or Camera RAW format. Ensure that all of the opened images are of the same source series. No other image files should be open in Photomatix except for the images you wish to combine. You will get weird results if images from different series are open at the same time.

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These 8 images from a massive manual bracketing series covering a dramatic exposure range will be combined into a single 32-bit High Dynamic Range image.

Highlight HDR from the program menu and select Generate. The following window appears:

Alternately, you can open your images to be merged to HDR by following the command path HDR>Generate and select the “Load Images” option to import images for HDR Generation.

Click OK once you have determined that the open images are all supposed to be part of the HDR generation process. The following window appears:

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Use the default setting for the response curve, and check “Align Images” if there’s a chance the images are not perfectly aligned.

Click OK, and Photomatix will merge the images into a 32-bit HDR. Once the HDR is generated, the progress box disappears, and your 32-bit HDR source file displays, along with the preview window, which shows the default tonemapping settings. Don't worry if this image doesn't look great; your monitor cannot accurately display the 32-bit data:

The true 32-bit HDR image cannot be displayed in all its 32-bit glory, but the HDR viewer (upper left) gives a sneak peak at what tonemapping will be able to do when the HDR is processed.

At this point, it is a good idea to save your 32-bit HDR, so you can apply different tonemapping settings to the HDR without regenerating an HDR each time you wish to retry tonemapping.

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This 32-bit HDR image, generated from 8 images from the A_Lantern series, is saved in a subfolder of its source images entitled A_Lantern_HDR_and_XMP.

We’ll save tonemapping settings in Extensible Metadata Platform format in this folder during the next step of this tutorial.

Tonemapping the HDR for output: Details Enhancer Method Photomatix Pro incorporates two 32-bit compression methods, Details Enhancer and Tone Compressor. Let’s walk through the Details Enhancer process first. Make sure the freshly generated (or freshly opened) 32-bit HDR image is the active window in Photomatix Pro and follow the command path HDR>Tonemapping. The following window appears:

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This is where HDR imaging really comes to life. The preview window shows what the final output image will look like once the expanded tonal range of the 32-bit HDR image is translated to conventional 8- or 16-bit space. Clicking on a point in the preview offers a 100% scale view of that section of the image.

The tonemapping preview window defaults to the Details Enhancer function, which incorporates several image quality adjustment sliders. Experimentation is truly the best way to gain an understanding of what each adjustment has on the image: • Strength: controls the strength of both local and global contrast enhancements. • Color Saturation: controls the saturation of the image. Each channel is affected equally. • Light Smoothing: controls smoothing of light variations. Higher values tend to minimize halos and give a more natural look to the image, but lower values tend to be sharper. • Luminosity: controls the compression of the 32-bit tonal range. Positive values boost shadow detail and overall image brightness. Negative values may appear more natural.

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• Micro-contrast: Sets the level of local contrast settings. Photomatix Pro suggests that (2) is often the best choice. • Micro-smoothing: smoothes out local details enhancements. The higher the value, the more noise reduction it applies. • White Clipping and Black Clipping: sets the minimum and maximum output values. White Clipping controls maximum values, while Black Clipping controls the minimum values. Setting White Clipping to 0.00% and Black Clipping to 5.00% results in an overall darker image with a more traditional LDR image tonality range, while setting White Clipping to 5.00% and Black Clipping to 0.00% will result in an image that appears overexposed with very flat contrast. For HDR imaging, neither extreme is desirable, so experiment with middle values on one or both. Make adjustments to the sliders until you are satisfied with the results. At this point, you may save your settings by clicking on “Save” at the bottom of the preview window. The image settings will be save as Extensible Metadata Platform files suffixed .xmpand these should be saved alongside your HDR source file, in this case, in the A_Lantern_HDR_and_XMP subfolder of the A_Lantern_Series1 folder which holds the LDR source images. The same settings can then be loaded in via the Load button, to apply the same settings to another HDR image. Select either 8- or 16-bit output in the upper-right of the preview window and click OK to output a traditional bit-space image with the expanded tonal range of a true HDR image. Depending on the image size and your hardware configuration, this may take a few moments. The tonemapping preview window disappears, and is replaced by your HDR output image, which can then be saved as a JPEG, TIFF, or PNG file. You can then open this file with your regular image editing software for traditional digital image adjustments. (You'll notice part of the tripod is visible in the very lower-right of this image. We’ll remove this with cloning tools in Adobe Photoshop CS2.) Save the output image in a new subfolder of the source images with a logical name, in this case: A_Lantern_HDR_Results There is no JPEG compression option at Saving. On a Macintosh, it can be changed under File>Preferences, and on a PC, under View>Default Options.

Tonemapping with Tone Compressor Follow the above directions to the opening of the tonemapping preview window.

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Click on the Details Enhancer drop-down menu and select Tone Compressor. The window will look almost identical, except that some of the slider adjustments have different names to represent the Tone Compressor algorithms. • Brightness: affects the tonemapping in relation to the overall image brightness • Tonal Range Compression: controls how the tonality of the 32-bit image is compressed into the 8-bit space of monitors. A higher values squeezes both shadows and highlights more towards the center of the histogram. • Contrast Adaptation: adjusts the overall HDR contrast. • White Clipping and Black Clipping: sets the minimum and maximum output values. White Clipping controls maximum values, while Black Clipping controls the minimum values. Setting White Clipping to 0.00% and Black Clipping to 5.00% results in an overall darker image with a more traditional LDR image tonality range, while setting White Clipping to 5.00% and Black Clipping to 0.00% will result in an image that appears overexposed with very flat contrast. For HDR imaging, neither extreme is desirable, so experimentat with middle values on one or both.

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On a technical level, Tone Compressor uses a Global Operator algorithm, while Details Enhancers uses a Local Operator algorithm. On a practical level, it has a different set of sliders to control the HDR processing of the output image.

As with Details Enhancer, adjust the sliders until you are satisfied with the results and click OK to output the HDR as either an 8- or 16-bit file with an expanded tonal range. And, as with Details Enhancer, you can save these settings to your Source_HDR_and_XMP subfolder. Name and Save the output image as a TIFF, JPEG, or DNG for traditional bitspace adjustments in your normal image editing program as described in the Details Enhancer walk-through. That’s it. That's the basic HDR generation and tonemapping workflow in Photomatix Pro. Congratulations! You’re well on your way to becoming an expert.

Other Cool Things in Photomatix Pro In addition to the true HDR generation and processing engines, Photomatix Pro comes with a handful of traditional bit-space exposure blending methods which live under the Combine menu heading. These are not true HDR processes, as they do not involve rendering a 32-bit image, and are therefore a bit out of the scope of this eBook. However, these techniques are so quick and easy to try that they’re worth mentioning. Simply open a series of source images and select an option from the combine menu drop-down: Average, H&S-2 images, H&S-Auto, H&S-Adjust, or H&S-Intensive, and Photomatix will blend the open images into a single merged exposure. Sometimes the results look great, other times, true HDR processing yields better results. But it’s so easy, there’s no reason not to try it. And these LDR exposure blending are included in a really cool feature of Photomatix Pro: Batch Processing.

Batch Processing with Photomatix Pro Almost all the functions of Photomatix Pro, from HDR Generation to tonemapping and Exposure Blending are included in the Batch Processor, which is found via the Automate>Batch Processing command path.

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You can automate a lot of the functions of Photomatix Pro via the Batch Processing window.

Check your options, select a source folder, select the "Under source folder" option, and then click run. Photomatix Pro can turn your source images into HDRs, Tonemap them, save the XMP settings, combine them using the LDR merging functions and more! Results will be saved to a subfolder entitled PhotomatixResults1.

Single File Tonemapping It isn't true High Dynamic Range Processing, due to the exposure range limitations of a single captured image, but Photomatix Pro can also Tonemap single Camera RAW or 16-bit TIFF files using both of its tonemapping algorithms. With a light touch, this acts like a shadow recovery filter and with some major tweakings, can make a single image look almost like it’s the result of a bracketed series.

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Adobe Photoshop CS2 Workflow HDR generation and processing is built into Adobe Photoshop CS2 and Adobe Bridge, so if you already own PSCS2, you don’t necessarily need to purchase a new software title for HDR processing. Adobe Photoshop CS2 is very expensive (at minimum several hundred dollars for a license), and these functions only ship with the full version; they’re not included in any version of Adobe Photoshop Elements. Nonetheless, a limited-time trial version of the program may be downloaded at www.adobe.com for both Macintosh and Windows operating systems. Adobe Photoshop CS2 doesn’t allow "pseudo-HDR" processing of a single image, or of a post-processed psuedo-bracketed series from a single image. The source image series for HDR generation with Adobe Photoshop CS2 should have a good degree of difference in exposure values between the images. You want at least three full stops between the underexposed and overexposed image, to be safe. You’re going to work on three images from a five shot Auto Exposure Bracketing sequence in this tutorial.

HDR Generation with Adobe Photoshop CS2 Launch Adobe Bridge and Adobe Photoshop CS2. Open the logically-named LDR source image series folder into Adobe Bridge. For selecting source files, you want to use details view, activated under View>As Details because it offers exposure information alongside the thumbnail. Highlight the source images to be merged to a 32-bit HDR. Images may be JPEG, TIFF, PSD, or Camera RAW format. Follow the command path File>Open With>Adobe Photoshop CS2 to open the highlighted files into Photoshop CS2.

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Selecting the "As Details" view mode in Adobe Bridge shows thumbnails, along with camera exposure settings, which is very helpful for the HDR workflow. File>Open With>Adobe Photoshop CS2 opens the highlighted images into Photoshop. Or you can simply double-click any active image to open all highlighted images into Photoshop.

After the source images are loaded into Photoshop, follow the command path File>Automate>Merge to HDR to merge the open images into a single 32-bit HDR file.

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Make sure that only the images to be merged to HDR are open, and that all open images are of the same bit-depth and file type. Don't mix a Camera RAW with JPEGs to generate an HDR.

If there’s a chance the source photos aren’t perfectly aligned, select "Open Files" from the prompt box drop-down menu and check "Attempt to align images.” Click "OK" to generate a 32-bit HDR.

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Depending on the number of source images, the source image file size, and your hardware configurations, the Merge to HDR process may take a few seconds to several minutes.

It’s also possible to use Bridge to generate an HDR from the image thumbnails. From the Adobe Bridge Menus, select Tools>Photoshop>Merge to HDR.

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Using the Bridge Merge to HDR command brings you to the same point as Photoshop's Merge to HDR command, except that you don’t have the option to align the images when HDR generation is initiated via Bridge.

Photoshop then does background processing of the images, and when the processing’s done, the "Merge to HDR" window appears onscreen. The primary window shows a 32-bit preview and thumbnails of the source images, including relative exposure values of the source image. In this example, we’ve selected to merge images with relative values of -2, 0, and +4. The slider under the "Set White Point Preview" histogram can be adjusted, but we're going to trust Photoshop with the setting. The default bit depth setting is 32-bit. Clicking OK with this setting selected opens the 32-bit image into Adobe Photoshop CS2. The vast majority of commands and actions are grayed out and inoperative in 32-bit mode. But opening the 32-bit file into Photoshop lets you save the 32-bit image as a true, high-bit HDR, which can then have tonemapping processes reapplied to the same image in Photoshop or other HDR programs, without having to regenerate the 32-bit image each time.

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The thumbnails showing the relative exposure values of the source images are very helpful. Notice there are checkboxes for each source image, so you can activate or deactivate each one. You can load a series of five images for preview, but at this stage you’ll merge only three of the source images. We're using all three for this tutorial.

The 32-bit HDR loads into Photoshop, and displays onscreen, along with the LDR source images. If you explore the commands and image quality settings in Photoshop, you'll see very limited 32-bit support. Some Sharpening and Blur commands are possible, along with Photo Filters, Exposure, and Channel Mixer. But for the most part, 32-bit offers very few adjustment options. The whole point of opening the 32-bit image is to save it to a subfolder of your logically named source folder. In this instance, we’re naming the folder D_Penn_HDR_and_HDT, and the file HDR_D_Penn_3_source.hdr. The HDT represents Photoshop's 32-bit file setting format, which we'll add to this folder during the HDR processing stage.

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Apart from the opportunity to save the 32-bit file, you don’t have many image adjustment options for a 32-bit file in Adobe Photoshop CS2. The HDR gets adjusted during its transition to 8- or 16-bit space.

Once the 32-bit HDR image is saved, it's time to crunch all that exposure range data into a smaller bit space that can be displayed and printed with modern printers and monitors. There’s no button or command that intuitively brings you to the HDR Conversion window. Photoshop's HDR Conversion dialogue box only appears when you follow this command path: Image>Mode>8 bits/channel or 16 bits/channel.

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It's a little confusing that there’s no obvious command to process a 32-bit HDR in Photoshop CS2. The HDR Conversion dialogue box appears when the bit mode is changed from 32 bits to 8 or 16 bits.

If you don't want to save the 32-bit HDR file, you can skip the above steps and simply move from the Merge to HDR command to the HDR Conversion dialogue box by selecting 8 or 16 bit/channel in the Merge to HDR window.

Selecting 8 or 16 bit/channel after the Merge to HDR window appears allows you to get right to HDR processing, but you don’t get an option to save the 32-bit HDR image with this shortcut.

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HDR Conversion in Adobe Photoshop CS2 Follow one of the above steps to arrive at the HDR Conversion window, either by selecting 8 or 16 bit/channel from the Merge to HDR command, or by changing the mode of an open 32-bit image to 8 or 16 bits under Image>Mode>8 or 16 bits/channel. The HDR Conversion window opens, offering four types of image manipulation. Click on the arrow next to Toning Curve and Histogram to expand the dialogue box to view the Histogram and Curves control. • Exposure and Gamma: This functions much like brightness and contrast controls. • Highlight Compression: Selecting this option results in the automatic application of a tonal curve which minimizes highlight contrast and spreads contrast through the total tonal range. • Equalize Histogram: Choosing this option results in the automatic application of a tonal curve which attempts to equalize the peaks and valleys of the HDR histogram. • Local Adaptation: This is by far the most flexible and powerful of Photoshop's HDR Conversion engines. Local adaptation is applied to the image via the curves/histogram window, and allows for subtle adjustments to the local contrast. By pinning a number of points on the histogram, you can isolate and manipulate pixel values with a very small range.

Select Local Adaptation from the HDR Conversion window to get the most control over your HDR conversion. Don't be afraid to try the other processing options, although in most cases Local Adaptation is the best option.

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A very nice feature of Photoshop's Local Adaptation processor is the ability to click on a spot in the image to show where that pixel value resides in the curves control. This lets you precisely target local color and contrast controls. The circle on the Curves line indicates the value of the red post in the image (spot 3 in the info pallette), which lets you choose several control points and shows the original color value and adjusted color value of each of these points in the image (See previous page for image.) Clicking a pixel in the image preview indicates where these pixels reside in the image curve. Shift-clicking a point pulls up the info pallette and shows the original and adjustment color values for this point.

In this image, we’ve shift-clicked on three points: one’s in the sky, upper right; another’s in the shadowed concrete foreground; and the third’s on the nearest red post in the middleground.

Click a point in the Curves window to bend and pull the tonal range of the HDR image.

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Notice the particularly serpentine 16-point curve in the figure. This configuration works well for this specific image but the same curve can yield wildly different results in another image.

You can also adjust the radius and threshold of the Local Adaptation processing. Radius determines the pixel spread and Threshold determines the minimum difference in pixel values that are affected by the Local Adaptation. Setting one very high and the other very low tends to produce a colored pencil or pastelsoftened effect in the image. Experiment with the settings to achieve your desired effect. You’ll see a departure from the normal HDR style in this image but the slightly sketched look feels just right. When you’re satisfied with your HDR conversion settings, click OK. • Optional: Click Save to save the settings. The dialogue box should open to the same folder where you saved the 32-bit file, in this case D_Penn_HDR_and_HDT. HDT’s the only format option. Give the file a more descriptive name than the default "untitled.hdt" and save it alongside the 32-bit HDR file. Depending on the file size and your hardware configuration, the Conversion may take a few moments. A progress bar lets you know it’s being processed. When it’s finished, a new image window opens with the 8 (or 16) bit image.

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Crunching the HDR to a smaller bit space can take a few seconds to a few minutes, depending on the size of the HDR source image and your hardware configuration.

Although it’s now a normal bit-space image, the image window displays the original HDR source image file name with the HDR-format extension. However, clicking Save or Save as allows only 8 and 16-bit file formats. Save your image at this point in your logically named file and folder system for further processing in traditional bit space in your normal image editing program (which is probably Photoshop CS2). You’ll learn about that in an upcoming chapter.

FDRTools Advanced Workflow At first glance, FDRTools appears menacing. It has a very serious-looking Graphical User Interface that barely wears either a Mac or Win skin, and doesn’t have the warm and fuzzy feel of Photomatix or Photoshop (neither of which are particularly warm and fuzzy, mind you.) It’s a different user experience, but once you get comfortable with the program layout, you’ll be impressed by its capabilities. Unlike Photomatix and Photoshop, which offer few, if any, controls over the photomerging process, FDRTools offers a visual preview of exactly which source image is responsible for the data load into the 32-bit HDR at a given exposure range. You also have adjustable histogram sliders to change the blending point between the source images. It’s possible to load an entire LDR source image series into FDRTools, and then selectively add and subtract the source images you’ll merge to the 32-bit file during the HDR Generation process. What does all this mean in plain language? It means that FDRTools has a pretty effective automatic ghost-removal function built into its interface. If the blending points that FDRTools assigns to the source High Dynamic Range-Photography

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images don’t fix your ghosting issues perfectly, you can try to fix the ghosts by manually changing the blending points by activating or deactivating a given LDR source image or by changing the histogram blending points between source images. All the while, another program window shows a section of the unadjusted HDR or the HDR with default tonemapping settings at 100% view level. Yet another window shows a small preview of the entire image—all in real time. What this means, in even plainer language, is that FDRTools offers an amazing degree of control over the HDR generation process. FDRTools differs from the other programs in another significant way. It’s not a two-step process for HDR Generation, followed by tonemapping of the 32-bit file. FDRTools truly operates on the source files only once, and saves the 32-bit HDR image at the same time as it applies the tonemapping settings to the 16-bit output file. During the HDR and tonemapping preview modes, it’s doing scratchpad math on the thumbnails, Navigator preview, and the section of the image visible in the 100% preview window. So it’s possible to experiment with tonemapping settings, then toggle back to the HDR generation window, tweak your LDR source image blending settings, and then toggle back to the tonemapping preview to see what those HDR generation changes do to the tonemapping. It’s not nearly as confusing or complicated as it sounds (really). Although it’s a more fluid, single-step process with FDRTools, we’re going to divide the tutorial into two halves: HDR Generation, and tonemapping. Just remember, it’s always possible to toggle back and forth between the two functions to make adjustments at any step of the process.

HDR Generation in FDRTools Advanced 1.8.2 Due to its cross-platform Graphical User Interface (GUI) programming, normal drag-and-drop file open functions don’t work properly with FDRTools. This means files must be opened through the Open icon, or under Image>Open in the GUI itself. There’s no bounding program window with menu commands on a PC, and File>Open at the top of a Mac’s desktop works for the Finder, not FDRTools. It’s nothing to worry about, but it can be confusing at first. FDRTools supports these file types: Most Camera RAW formats, JPEG, TIFF, Radiance (.hdr), and Open EXR (.exr). Click the Open button and browse to the LDR source image series folder, and then highlight the first image to be merged together to generate the HDR. If you don’t see the desired source files or the files are grayed out, change the file type dropdown to the file format you want. Repeat this process until all of the desired LDR source images are loaded into FDRTools thumbnails preview window. As each image is loaded, FDRTools attempts to align the images automatically, if necessary. High Dynamic Range-Photography

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Once all the desired LDR source images are loaded, the main program window shows image thumbnails and each image’s histogram data. A second program window shows a small, whole-image preview of the unprocessed HDR. (Click the tabs at the top of the Navigator to toggle between unprocessed and Tonemapped HDR previews.) Use the slider bar at the bottom of the Navigator window to darken or brighten the preview. Clicking an area of the image in the Navigator window opens the 100% preview window. This image can be resized, if desired, although the larger it is, the longer the redraw time between each adjustment.

There are five images in this series, all currently active. The default “Average” photomerging process did a very good job of ghost removal overall, but there are a few minor issues we need to address. Notice the variations in the histograms to the right of each image thumbnail.

If the HDR preview looks good with the Average merging method, you’re ready for tonemapping. But for the sake of this tutorial, let’s take total control of photomerging with FDRTools’ Separation function. High Dynamic Range-Photography

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FDRTools did a great job of properly de-ghosting the truck in the preview window below, but upon close inspection of the preview, you’ll see some other minor ghosting issues with the pedestrians in the foreground, which, due to their size and position in the image, are more of a concern.

Switch from Average to Separation in the main program window to take control of the photomerging process. You can clean up the black spot on the truck later using cloning tools.

The sliders below each source histogram can be adjusted in Separation mode. Notice the change in the highlighted area of each histogram between this and the previous illustration, and the effect on the preview window. The truck is now halfinvisible!

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You can adjust the Exposure Transition Range slider below the HDR histogram (top of main window) to determine the smoothness of the transition between the active areas of each source image’s histogram.

Since attempting to fix other ghost issues ended up ghosting the truck, it’s time for another trick: reducing the number of source images. By unchecking the Include box on the second and fourth images, we’ll resolve the ghosting issues with the truck and other areas of the image.

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By removing two of the middle images, we’re not reducing the overall dynamic range of the image. We’re simply making an HDR image with fewer source images over the same dynamic range. Removing two of the LDR images will resolve almost all of the ghosting issues that this challenging scene presented.

Once the HDR preview and ghost fixes (if necessary) are satisfactory, you’re ready to switch over to tonemapping. Remember, FDRTools isn’t a two-step process, so it’s not necessary to save at this point.

HDR Processing with FDRTools Advanced FDRTools Advanced incorporates three tonemapping Algorithms for HDR processing. Simplex is described by FDRTools as a simple, but fast, tonemapper with poor contrast. This is simply for previewing the HDR with basic tonemapping settings. The only image quality adjustment sliders are Gamma, which affects the brightness curve, and Saturation, which increases or decreases the color saturation and white and black points on the histogram. Don’t expect much from Simplex. Click the tab to switch to Receptor or Compressor, which are more robust and yield better results. High Dynamic Range-Photography

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Receptor is a global operator that produces smooth images, but is not as detailed as Compressor, according to the program’s pop-up description. • Compression slider controls Dynamic range compression. • Brightness affects image brightness. • Gamma affects the brightness curve. • Saturation increases or decreases the color saturation. • White and Black point sliders on the histogram affect white point and black point of the output image. As with the other programs, experimentation is a big part of the learning experience. Adjust each slider and observe the results to get a feel for each command.

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Click the Tonemapping button in the main program window to switch from HDR settings mode to the tonemapping process. Don’t bother with the Simplex Tonemapper. Experiment with Receptor (shown above) and Compressor to find the best tonemapping settings. Notice how the Navigator and 100% preview window have switched from the harsh true HDR preview to the softer tonemapping preview.

If you’re not happy with the Receptor results, try Compressor, which is the most powerful tonemapper in FDRTools. Compressor uses a local operator algorithm and can produce the most vivid, realistic results. Compression regulates the tonal range compression. For true bracketed HDR images, try settings from 5-10. For pseudo-HDRs and single-image tonemapping, it’s best to use settings below 5. Contrast is the primary determiner of image contrast. Lower values produce smooth transitions between contrasting pixel values, while high values emphasize local and global contrast. • Smoothing modifies the Contrast settings. • Brightness affects image brightness. • Gamma affects the brightness curve. • Saturation increases or decreases the color saturation. • White and Black point sliders on the histogram affect white point and black point of the output image. This example (bracketed over a large dynamic range), achieved pleasing results because of high values for Compression, and Contrast and Smoothing, combined with a black point adjustment towards center and a slight bump in the saturation. Again, experimentation is a major part of the tonemapping process. These same settings may not produce similar results in a different image. Go ahead and experiment with the settings.

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High values for the Compression, Contrast, and Smoothing along with a black point adjustment and saturation boost produced pleasing results. We’ll now save the 32-bit HDR and 16-bit Tonemapped results for final image quality adjustments in Photoshop CS2.

Saving the HDR and LDR output image in FDRTools Advanced Once you’re satisfied with the tonemapping adjustments, click Save to save both the 32-bit HDR image and the 16-bit tonemapped HDR output file at the same time. Click the top Browse button (next to HDR Image) to select a location to save your files. A prompt box appears. Type in a logical folder location and file name. In this example, the folder’s named E_Streetcorner_HDR_and_LDR_Results. This is a subfolder of the source image folder. The 32-bit HDR is titled E_Streetcorner_HDR_32bit_from3.hdr. The 16-bit output image name will autofill with the same name, with the TIFF extension. The autofilled name is changed to E_Streetcorner_HDR_lowbit_from3.tif to better represent the file in the LDR line. Below the save commands is a great feature—the option to automatically open the 16-bit output file into your normal photo-editing program for post-processing.

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Check this option, and select the program to open the output file, if you want to move right to post-HDR fixes. Click Run and the FDRTools saves the HDR and LDR output image. A progress bar shows the status of the processing, and the bottom panel of the Save window slowly fills up with technical information about the processing being done to the images. It’s very technical, but some of the information gives a glimpse into what’s actually happening to the pixels and photos as they get crunched and processed.

After you click run, the bottom panel of the Save window fills up with all the computer processes taking place.

Once the progress bar finishes, check your folder to make sure the files have been saved, and your output image is ready for final touch-ups in Photoshop.

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Software Comparison: Which HDR Processor is right for you? Each of the three programs we’ve looked at has its own charms and quirks. The route that each takes along the journey from HDR Generation to Tonemapped Output follows a different path to arrive at the same point. Is one method far and away superior to the next? Not better—just different. We won’t call one program the winner and another the loser in this comparison. Instead, you’ll learn the strengths and weaknesses of each program, and from the user profiles described, you can pick the program that’s best for you. What if you don’t exactly fit one profile, or you fit somewhere between two profiles? Great news! There are fully functioning demos of each program available. Download the program, give it a spin, and it if works for you, purchase a license. If not, try the next one! Photomatix Pro Price: $99.00 Download: www.hdrsoft.com User Profile 1: The HDR beginner. Although the workflow’s a little confusing at first, overall it’s much less confusing than the other programs. A cleanly designed tonemapping preview window with slider-based adjustments and a large preview offer an easy way to visually learn 32-bit tonemapping. User Profile 2: The HDR power user. The batch processor allows for background HDR generation and tonemapping of folder upon subfolder of LDR source files. For the hardcore HDR photographer, the program is worth the money simply to automate the HDR generation process. Photomatix Pro is a free-standing program with support for many types of LDR input files. It also supports many of the standard 32-bit formats. The HDR Generation mode offers only a few user options, including automatic image alignment or user-adjustable image alignment. HDR Generation and tonemapping are two distinct processes. There are two tonemapping processes: Details Enhancer, which uses a local operator algorithm for localized contrast enhancements, and Tone Compressor, which uses a global operator algorithm to adjust overall tonal compression and contrast. Both tonemapping processes reside in the preview window, and image quality adjustments are controlled by a series of sliders with optional numeric High Dynamic Range-Photography

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boxes associated with each slider for precise file input. The slider-based adjustments and large preview offer an easy, visual understanding of the process for the HDR beginner. Tonemapping settings can be saved and loaded during the tonemapping preview stage or immediately following creation of the HDR output file, in Extensible Metadata Platform format. In addition to the true 32-bit processes, Photomatix Pro includes a handful of low bit-space exposure blending tools, which sometimes produce results on par with the Tonemapper. Psuedo-HDR imaging is possible by converting a single image to 32-bit format for tonemapping. Additionally, Photomatix includes a batch processing engine, which can automate almost every exposure blending command in the program: from HDR Generation through tonemapping and the low-bit blending methods. This engine is useful for running a long series of LDR source images through HDR Generation because that can take a while, especially with large source files on a slow computer. The weakness of the Batch Processor is that there’s no tonemapping preview available. Batch Processing does, however, save the .XMP info for each process, and this info can be loaded into the tonemapping preview window to give a starting point if the Batch Processing results aren’t perfect. For the HDR power user, Photomatix Pro is worth the price simply for the automated HDR Generation function. Adobe Photoshop CS2/CS3 (Beta) Price: $649.00 Download: www.adobe.com User Profile 1: A pre-existing Photoshop CS2/CS3 (Beta) user who wants to give HDR Processing a try within the Adobe family of programs without having to download new software. User Profile 2: Post-processing output experts who absolutely love the subtlety and fluidity of Curves control. User Profile 3: The early adopter. The hardcore Photoshopper who wants to be the first to download and experiment with the newest beta to see how it compares to the previous version and post his findings to an online forum or blog. Adobe’s HDR Generator and Processing engine ships with Adobe CS2 and CS3 (Beta), so there’s no extra software to purchase if you’ve got a full Photoshop CS2/CS3 (Beta) license. Of course, Photoshop sells for $649.00, which is quite steep compared to the other programs. Unlike the other programs, though, High Dynamic Range-Photography

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Photoshop isn’t a single-purpose program. It’s the industry-standard photo editing and imaging platform for publications large and small, newspapers, and fine artists. It’s the 800-pound gorilla of the image editing arena. The HDR functions are but one facet of this program. Is the HDR engine of CS2/CS3 (Beta) worth $600 more for the Photoshop Elements fan who wants to give HDR a try? Probably not. But Photoshop CS2/CS3 (Beta) does offer an amazing set of imaging tools as part of its total package. Still, if you’re comfortable with PSE and are considering upgrading solely for HDR processing, there are more economical HDR programs available. As for Photoshop CS2’s HDR processing, it does a good job of merging the source images with the alignment option, if hosted through Photoshop rather than Bridge. CS3 (Beta) adds an automatically-activated alignment process if Bridge is the HDR generator. Aside from activating a few more global adjustment options under the image menu and filter menu, HDR generation and processing is virtually identical in these two versions. In either CS2 or CS3 (Beta), the Local Adaptation curves control is the most powerful tonemapping tool. Controlling curves can be a challenge for the digital imaging beginner, but the ability to pin multiple points and highlight and pinpoint exact reference colors on the curve for localized adjustments makes for a very powerful tonemapping tool that offers a great degree of control. FDRTools Advanced Price: EURO 39.00. US price based on current exchange rate. Download: www.fdrtools.com User Profile 1: The methodical, detail-oriented photographer and digital expert who wants total control of each and every step of the process. Aside from being able to de-ghost the HDR source image, FDRTools allows the user to design input and output device profiles. This FDRTools user has a monitor calibrated to work with her camera and printer, and expects nothing but the same from an image editing program. User Profile 2: The risk-taker. The sort of photographer who holds his breath and handholds a bracketed source image series with moving objects in the hope that he and his software are skilled enough to overcome the obstacles. This software is up for the challenge. Are you?

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User Profile 3: The budget-minded photographer who isn’t afraid of learning a new software interface. Of the three programs, this is the most economical choice. FDRTools is the most economical of the three programs, but that doesn’t mean it’s cheap. Despite its modest price, it's the only of the three programs that allows such an amazing degree of control over the HDR Generation process. The mostly effective Ghost remover function allows experimentation with new subject matter areas with moving elements to open a whole new world of shooting opportunities for the HDR photographer. The two robust Tonemappers—Receptor and Compressor—are equal to their competitors in caliber. Plus, the ability to hot-swap between tonemapping and HDR Generation to make adjustments to the input and output previews by using scratchpad math and partial renderings is an impressive programming maneuver. The beginner may be a little intimidated by the layout because of the overlaying histograms and overall program interface. But honestly, beneath the hard-edged exterior lies an extremely elegant, well-designed program whose deviation from the normal 2-step HDR process provides an exciting and interesting element to the HDR program arena.

Final Image Adjustments of your HDR Output Image Even the best tonemapped image benefits from some final image adjustments in a regular bit-space program, such as Adobe Photoshop CS2 or Adobe Photoshop Elements 5. The tonemapping process should do the majority of the work, and a light hand in Photoshop to add the finishing touches is usually all that’s needed. Post-processing your HDR output image in Photoshop differs little from prepping a normal single shot image with basic digital darkroom techniques. We’re dealing with a single-layer file here, although many of the processes can be applied to an adjustment layer, if that’s more comfortable for you. We’re working in Photoshop CS2, although most of the commands and functions are also in Elements, perhaps with a slightly different interface. We’re going to prep the street scene from the FDRTools tutorial for display. You’ll work with the full-sized image, and will downsample for web display as a last step. Open your HDR output image into Photoshop. As the image below shows you, there’s a great tonal range with amazing detail, but the overall feel is a bit flat.

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This is the output file from FDRTools, which appears a bit flat.

We’re going to start by adjusting the overall levels, which lack white and highlight values due to the HDR processes. We’ll pull the white histogram point just to the edge of the curve to squeeze the tonal range and brighten up the photo. Image>Adjustments>Levels opens the Levels controller.

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Depending on your image, you may have to adjust both the black point and the white point.

Next, we’ll open up the middle values a touch by pushing up the center point of the image curve. Image>Adjustments>Curves opens the Curves controller.

A 1/4-3/4 S-Curve boosts overall image contrast.

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Remember the black ghost on the armored truck? A quick pass of the Cloning tool (rubber stamp) cleans it right up. You may also want to try the healing brush (band-aid symbol) which can also clean up image imperfections.

Clean up image imperfections after HDR processing in your regular imaging program, so that you’re working with only one file. It’s much easier this way.

The idea for this photo is to even out the exposure elements with HDR imaging, and crank up the color to bring a bright, yet gritty, color palette to this nondescript corner in midtown Manhattan. To achieve this, let’s push the saturation up to +52 with the Hue/Saturation adjustment controller, which is opened through Image>Adjustments>Hue/Saturation. Next, we’ll save a full-sized version by appending _Full_size_prepped to the existing file name, and downsample a web display version to 6 x 9 inches at 72dpi and append _screen_sized_prepped to the file name. That’s all the post-processing required for this image. The screen-sized version is now ready to be shared online. The full-sized version gets archived for eventual printing. When you’re ready to print, make a series of test strips from the image, applying different Sharpening High Dynamic Range-Photography

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and Noise Reduction settings, along with the non-sharpened, non-noise reduced master file and compare which version works best for print output. With many HDR output images, especially when using Local Operator algorithms, the tonemapping process introduces enough sharpening to the image. The additional application of UnSharp masking can degrade the overall image quality. Experimentation really is a major part of the HDR imaging experience. Don’t be afraid to put an HDR output image through your normal post-production workflow, but at the same time be flexible and notice what’s happening to the image. Does it want sharpening or noise reduction? Would it look better with a selective desaturation? Go ahead and experiment, but remember that HDR processing is the biggest part of the equation.

This is our vision for this image.

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Final Thoughts • The single most important aspect of HDR imaging is bracketing your exposures to capture the scene all the way through. The imaging and processing technologies are getting better at ghost removal and image alignment, but always try to use a tripod for the best results. • HDR imaging is a very exciting imaging technology, and is still in its infancy. In the coming years, there will be more support for 32-bit file formats, and the tonemapping algorithms should improve with each program upgrade to provide even better HDR tonemapping options and controls. • You’ll soon develop an HDR eye, and recognize scenes that’ll work well with HDR imaging, due to the tonal extremes, combined with texture and color contrasts. Not every image turns out amazingly well with HDR, but hopefully after a few tries, you’ll find it easier, both in composition and in processing. • HDR programs are going to continue to advance in features and processing. This cool new imaging technology is bound to have a major impact on digital imaging in landscape, architectural, fine art, and commercial arenas, as it becomes easier to understand and programs become even more robust. • As the programs evolve, and ghost removal processes improve, even more of the world will be open to the HDR view of things. That should offer new opportunities to capture and share your unique vision of the world. • You can’t go wrong with any of the three programs featured in this book. If funds aren’t an issue, buy all three! But if you’re on a budget, take each for a test drive and pick the one that works for you. • If we’ve achieved our goals, you’re both excited and informed about the possibilities of HDR imaging. Always remember to bracket your shots, keep the camera still, and enjoy the process from start to finish!

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All photographs in the book were captured with the Pentax K10D DSLR, with the SMC P-DA Pentax 10-17mm f/3.5-4.5 fisheye lens. Thanks to Geraldine Joffre of Photomatix, Andreas and Manfred Schomann of FDRTools, and all the good folks at Adobe and A&R Edelman for technical support. Thanks to my colleagues at Popular Photography & Imaging, American Photo and www.PopPhoto.com. Thanks to Mark Lent, and my brother James, for early technical edits of the rough pencil sketch version. Thanks to Phil Ryan for a thorough tech and copy edit of the first final draft. Thanks to my mom and dad, who raised us in a house filled with photographic inspiration, and who supported all my creative endeavors. Thanks to Steve Weiss at O’Reilly for letting me take this idea and run with it. And most of all, my most humble thanks to my wife, Corey, who is patient, supportive, brilliant, and beautiful, and who is now an accidental expert in all matters of HDR imaging, as well.

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