Discovering Hidden Color

One of the primary benefits of working in the Lab colorspace is the ability to make very dramatic adjustments to color without affecting luminance. Take a look at the image below, which is pretty much straight out of the camera, a Sony NEX-7. (Click on the images to see them larger. It helps with this discussion.) While it appears dark and drab, you can see there’s some reddish-brown in the structure. When I saw them live, the hanging lights appeared pure white. But as you can see, they not only have a bit of color, but the color appears to vary from light to light.

 

My goal was to enhance the colors and to create a holiday red-and-green look to the scene. At the same time, I wanted to maintain the green in the small Exit signs. (Yes, you need to click and look at the larger version!)

Lab colorspace to the rescue!

The image below shows what I was able to do with not much more than a Curves Adjustment Layer in Photoshop in the Lab colorspace. I anchored the a & b channels at the zero-zero crossover point. I then steepened both a & b quite a bit to enhance the existing color. From there, I played with the a channel (green-magenta) until I got close to the red and green I was looking for, then added a bit of yellow in the b channel (blue-yellow).

By enhancing the color contrast I was able to bring out the shape and depth of the architecture. I was also able to turn what appeared to be white lights into an array of multi-colored ones. What you’re seeing in the lights is a substantial amplification of the color variations, thanks to very steep a & b channel curves in Lab color.

Note: I also used the ALCE v2 plugin (radius=180) to enhance the local contrast and emphasize the structure of the building.

Lab Color and My Workflow du Jour

I’ve lately been talking about photo post-processing workflows on various podcasts, Google+ hangouts, classes and workshops, which has generated a lot of questions and requests for more info. It’s my workflow du jour because I’ve never had a single workflow that’s lasted for more than a few weeks. By the time you read this, it will already be out of date. For that matter, I don’t really have a formal workflow since every image is different. But I’ve developed a default sequence as the starting point for most of the images I shoot. At least for this week.

I spent some time debating whether I would publish this blog post or not. I’m actually a bit nervous about telling everyone about some parts of the workflow — not because I want to keep them secret, but because I fear you will go directly to the shortcuts I recommend without taking the time to understand the concepts behind them. You can get pretty good results without studying the underlying theories, but you’ll be shortchanging yourself. Obviously, I’ve decided to go ahead with this post in the hope the tools not only simplify your post processing but also encourage you to dig deeper into how they work and how they can be further manipulated.

I should also point out that there’s nothing of my own creation in this workflow. Everything I’m using I’ve learned from others who know a lot more about post processing than I do. Towards the end of this article I’ve linked to the original work of my personal workflow gurus so you can learn directly from the sources.

What Are the Prerequisites?

Although much of my workflow uses automated Photoshop actions, some of the steps must be done manually. This is not for Photoshop newbies. Before utilizing any of the tips and tools in this article, you should first learn the following aspects of Photoshop:

  • selections
  • layers and layer masks
  • channels
  • curves
  • the Image->Apply Image… menu feature

What Are the Shortcuts?

My workflow du jour uses two Photoshop plugins. The first is Dan Margulis’ free Picture Postcard Workflow Panel shown below on the left. (The name is cute but misleading. It’s not just for a picture-postcard look.) The panel automates many of the steps in Dan’s Picture Postcard Workflow, which if done by hand not only make for a complex process but can’t be performed by mere mortals without pages of notes. You can really get yourself into trouble with this tool, but you can also achieve amazing results in no time at all once you get the hang of it.

The second Photoshop plugin, shown on the right, is the Channels Power Tool (€20). This is a tremendous timesaver for identifying and swapping channels and applying them as layers and masks such as in Lee Varis’ 10-Channel Workflow.

What About Lab Color?

Much of my current workflow is based on the Lab colorspace, which I’ve been using on and off for about 2.5 years. I first wrote about Lab color in 2010, specifically in conjunction with HDR. I stopped using Lab color for a while because I didn’t fully understand it. Although I’m still learning and experimenting, I now believe I’ve achieved a deeper comprehension of the true potential of working in this colorspace.

You’re probably familiar with the RGB colorspaces in which there are three channels: red, green and blue. Your digital camera records images in RGB and your browser displays images using RGB. When an image is printed using offset press inks, it’s converted to the CMYK colorspace with cyan, magenta, yellow and black channels.

Consider how you change the brightness or luminosity of an image in RGB or CMYK. In RGB you increase the levels of all three channels. 100% red, green and blue gives you white. 0% results in black. In CMYK, you reduce the amount of ink in all channels in order to get to white, the color of the underlying paper. But the problem with both RGB and CMYK is that there’s no way to change the luminosity of an image without also changing the hue and/or saturation of the colors.

When is Lab Better Than RGB or CMYK?

Lab is just another colorspace like RGB and CMYK, but it separates luminosity from color. There are three channels: The “L” channel controls luminosity but has nothing to do with color. Conversely, the “a” and “b” channels control only color and don’t affect brightness. The range or gamut of the Lab colorspace is huge. Not only can it represent every color of RGB and CMYK, it can also represent colors that are beyond reality. (Try to imagine a yellow that is simultaneously very saturated and as dark as pure black.) Lab is also an extremely accurate and standardized colorspace. Whereas we all need to calibrate our RGB monitors and adjust for our printers, papers and inks, the colors in Lab are precise. For example, when an automobile body shop wants to exactly match the color of your car’s paint, it uses the Lab color specified by the car’s manufacturer.

Unlike RGB and CMYK, the Lab colorspace is designed to approximate human vision, which has a powerful ability to segregate colors. For instance, we can perceive variations in green leaves where there may be very little luminosity difference. The channel structure of Lab allows us to manage both luminosity contrast, with which we’re all familiar, and (separately!) color contrast. The latter concept may be new to you. In RGB we have little opportunity to adjust the contrast of various colors, but in Lab color mode we can do just that. Photographs can often be improved by increasing the color contrast in order to enhance those differences.

Lab’s a and b channels specify opposing-color axes that you can visualize as a color wheel. The a channel specifies the green/magenta axis while the b channel represents the blue/yellow axis. (The image below is a bit misleading because it doesn’t show the variations from the center to the edges. Unlike RGB and CMYK, these are variations of pure saturation, not combined with luminosity.)

[CC-BY-SA-3.0] via Wikimedia Commons
When you add a curves adjustment layer in Lab color you can do things you’d never be able to accomplish in RGB. For example, you can warm up the saturated blue portions of your image without affecting the other less-intense blue areas, and do so without ever creating a layer mask. You can increase the contrast in the greens without shifting the overall cast of the image. It takes a while, but once you get the hang of it, working in the Lab colorspace is extraordinarily powerful.

Why Should I Use Lab Color in My Workflow?

Let’s start with an example. Below are three versions of a single image.

The above image is pretty much straight out of the camera. Note a few problems:

  • There’s a blue cast in the shadows.
  • There’s relatively little contrast either in luminosity or color.
  • The lack of contrast makes the image look flat and lacking in depth and detail.

The second version above is typical of what you can achieve with basic Photoshop skills. The color and contrast are somewhat better, but there’s still a blue cast to the shadows.

The final image above is the result of spending no more than five minutes tweaking in the Lab color space. I was able to remove the blue cast from the shadows as well as increase both the luminance and color contrasts.

Did I correct this image using only plugins and clicking on buttons? No. In this case I had to resort to creating curves in Lab color mode and to changing the opacity of various layers. Although I made all the changes to this image in less than five minutes, I did rely on some of these more fundamental and manual operations. I mention this as an example of why the shortcuts alone are often insufficient and why you need to learn the underlying concepts.

So What’s Your Workflow du Jour?

As of today, here are the steps I follow for many of my images, particularly landscapes, cityscapes and abstracts. Product shots (in which colors need to be accurate), portraits or other photographs that feature faces require a rather different approach and aren’t addressed here.

  • I process the RAW file in Lightroom.
    • Camera Calibration (I’ve created dual-illuminant profiles for each of my cameras.)
    • Lens Correction
    • Default Sharpening (minimal; just the equivalent of what the in-camera JPEG processor might do)
    • Noise Reduction
    • Chromatic Aberration removal
    • White Balance (overall correction)
    • HDR Merge: If it’s a multi-exposure HDR image, this is the point at which I use Photoshop’s Merge to HDR Pro and bring a 32-bit merged HDR image back into Lightroom. I make no adjustments while in Photoshop at this stage. [video]
    • Tonality: The goal here (still in Lightroom) is just to squeeze everything into a narrow dynamic range. RAW files and 32-bit HDR images typically have too wide a dynamic range and will need to be tonally compressed or tonemapped down to 16-bit RGB. I adjust the exposure, contrast, highlights, shadows, whites and blacks to create a low-contrast image in which everything (including highlights and shadows) is away from the edges of the histogram. My objective is a technical one, not to make the image look good yet.
    • Stop There: I do not use clarity, vibrance, saturation or anything else in Lightroom if I’m going to use the rest of this workflow.
  • In Photoshop, I start with a 16-bit RGB image from the above steps.
    • I perform any retouching other than color corrections.
    • Save this version as a .psd file with all layers in case I need to revert to this stage.
  • Dan Margulis’ Picture Postcard Workflow (PPW)
    • Using the Photoshop PPW Panel, I start at the top and work my way down, typically (but not always) using the actions listed below. For each action, I experiment with the visibility and opacity of the layers until I get the look I want. Occasionally I add a layer mask if the effects need to be localized. This is where it’s really helpful to understand what the PPW actions are doing behind the curtain.
    • Bigger Hammer for tonal contrast.
    • Switch from RGB to Lab color mode.
    • Color Boost and/or the Modern Man from Mars for color enhancement and contrast.
    • 2012 Sharpen
  • Lee Varis’ 10-Channel Workflow
    • If I can’t get the results I want using Dan’s PPW, I return to the pre-PPW saved .psd. I haven’t spent a lot of time in PPW so far, so I don’t worry about throwing away my work.
    • I use the Generate Preview button on the Channels Power Tool panel to look at all ten channels available from the RGB, CMYK and Lab colorspaces.
    • I use one or more of the channels to replace others or as luminance mask to bring out detail or color.
    • Once I’ve done the best I can using individual channels, I take the image through Dan’s PPW.
  • Final Touch-Ups
    • After all of the above (particularly sharpening) all my sensor’s dust spots magically appear, so I often make another cleanup pass at the end.

Where Can I Learn How to Do This?

You can download Dan’s PPW Panel and start using it immediately, but as I wrote at the beginning of this article, you’ll be far more effective if you invest the time to understand how the various actions work and Lab color in particular. The PPW Panel includes extensive Help files, but they’re not the best place to start. The Help file for Dan’s 2012 Sharpen action alone is 23 pages long.

Unfortunately, there’s a huge gap and a steep learning curve separating the use of the shortcuts and truly understanding how they work. Here are my recommendations (in order) of the resources you might use to learn about channels, Lab color and the rest of these workflow concepts:

  • Mark Lindsay teaches and writes about Lab color and related techniques. Mark has posted some of the best introductory articles, but he hasn’t yet gone very deep into his workflow. His articles include:
  • Check out Lee Varis’  Professional Photshop Toolkit. In addition to Dan’s PPW Panel, Lee’s toolkit includes:
    • Free videos covering Lee’s 10-Channel Workflow and many other topics. At this point you’ll be into swapping channels, using channels for masks and blending modes. You may never make another selection by hand again.
    • You’ll want to get the Channels Power Tool (€20). This is almost mandatory for Lee’s 10-Channel Workflow.
    • The False Profile Panel (free) is another plugin you’ll occasionally find useful once you get this far.
  • Download, install and use the latest Picture Postcard Workflow Panel for Photoshop. This automates most of what you’ve learned so far. Click on the Help button and read all of the associated PDF files. You’ll be busy.
  • Take a break from Dan’s extensive Help files, sit back and watch his videos on Kelby Training. If you’re not already a member, I suggest you sign up for one month (US$24.95) during which you can watch all these courses. It will be some of the best $$ you spend on photography.
    • Start with Introduction to Photoshop Lab Color.
    • Next, watch The Lab Frontier.
    • Work with what you’ve learned from Dan and try the techniques as explained by Mark Lindsay above.
    • Come back to Kelby and watch the courses on the Picture Postcard Workflow Part 1Part 2, and Part 3. These explain the manual processes of the PPW but pre-date the release of the PPW Panel.
  • You now qualify as an Lab color geek. Go directly to Dan Margulis’ Lab color bible, Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace. This will keep you really busy for a very long time!
  • For extra credit, now that you know all about channels, take your knowledge back to RGB and explore Tony Kuyper’s treatise on Luminosity Masks. (Note that the first steps in Margulis’ PPW are done in RGB, so Tony’s concepts work well here.)
What’s Next?

You’ve got to be kidding! It will take you months to get through the resources I’ve outlined above. And then you’ll want to go over them again to truly nail down the concepts. In any case, this is the point to which my knowledge of Lab color has progressed as of late November 2012. I’m in the process of my second pass through everything. It’s geeky, but it works for me. I hope it works for you as well.

As you have questions or learn of additional resources, please leave a comment and I’ll use it to update this page.

Updates

  • 11/25/12: Scott Loftesness and I have been collaborating together on this Lab-based workflow stuff for the past few weeks. Each of us has tried one technique or another, then to have the other adopt and improve on it. It’s been a valuable, mostly remote collaboration. Because these techniques can be so confusing at first and the learning curve so steep, I recommend you also find someone with whom you can study/learn with. More than once, Scott and I have needed the other to either explain a technique or at least remind the other what it was we’ve already learned. Scott has just posted an example of his own workflow du jour and it contains some very specific steps. I’m still digesting them myself and will see if I can (a) understand them, and (b) merge them into my own processes.
  • 11/25/12: Since posting the original article only two days ago, I’ve added the free Advanced Local Contrast Enhancer (ALCE) Photoshop plugin by Davide Barranca to my workflow. It’s like Lightroom’s Clarity feature, but on steroids. Make sure to check out the excellent video tutorials by Marco Olivotto.

HDR Workflows

Update 1/19/12: Based on feedback from many including John Omvik at Unified Color, I’ve improved my #1 workflow and substantially edited all the workflow descriptions below.

This is my first-ever high-dynamic-range (HDR) image, shot nearly three years ago. Since then my HDR workflow has changed quite a bit — almost weekly, it seems. As I’ve recently been running tests on some aspects of HDR processes and tools and particularly methods for transferring images between applications, I thought this would be a good time to pin down and document the workflows I’ve been using and explain why I’m still using them or not.

My primary applications are Adobe’s Lightroom (LR) and Photoshop (PS). I use LR to organize my images and for basic processing. I turn to PS for images that require adjustments beyond LR’s capabilities. The HDR tools I’ve used at one time or another include Photomatix ProLR/EnfuseHDR Efex ProHDR Expose 2 and its cousin, 32 Float. Note that all of these applications are available as free-trial versions. I encourage you to download them and experiment with these workflows.

Because you may not have some of these applications, I’ll describe seven different multi-image workflows as well as some for single-image HDR. My goal is to cover not only the tools and methods I’m currently using, but also those that I tried, tested and in some cases abandoned before settling on my current choices.

Workflow #1: 32 Float (with Photoshop)

I’ve recently started using Unified Color’s 32 Float for most of my high-quality HDR images. 32 Float is a PS-plugin version of HDR Expose. Given that I usually end up in PS anyway, this gives me a simpler workflow than I’d get with HDR Expose. I’m only giving up batch operations and a few functions that are better performed in LR or PS anyway. This is my current workflow for my highest-quality HDR images.

  1. Unless you’re shooting action/sports, which rules out multi-exposure HDR anyway, always shoot in RAW. Otherwise none of this applies to you.
  2. In LR, make only two adjustments to your images: lens correction and camera calibration, which can only be done at this stage. Defer everything else until your RAW files have been merged into a single 32-bit image. (I have camera profiles for each of my body/lens combinations made using a ColorChecker Passport.) Use Copy/Sync to apply the same adjustments to all the bracketed originals. If you’re not an LR user, you can instead perform the equivalent of this and the following step using Adobe Bridge and Adobe Camera Raw (ACR).
  3. Select the bracketed RAW files in LR then (from the Photo menu or ctrl/right-click) Edit in…Merge to HDR Pro in Photoshop. Importantly, and unlike some other Edit in… and Export options, Merge to HDR Pro sends full-range 32-bit files to PS, even if you’ve made adjustments in LR. This launches PS’s own HDR Pro module. [PS’s tonemapping is weak, which is why all these third-party tools exist. But the merge-to-HDR function seems to work as well as any other.] In Merge to HDR Pro don’t be alarmed if you don’t see your highlight or shadow details. You’re only looking at a low-dynamic-range (LDR) preview of the HDR image, which can’t be properly displayed on your monitor.
  4. In HDR Pro set the Mode to 32 Bit and click OK. This merges the originals to create a 32-bit HDR image, then opens it as the Background layer in PS.
  5. Launch 32 Float from PS by selecting Filter…Unified Color…32 Float.
  6. In 32 Float tonemap the HDR image to low-dynamic-range (LDR). Many operations are best done here, while you’re in 32-bit mode and your luminance data are separate from your color data. Go ahead with global changes such as sharpening, noise reduction, local contrast and color and tone adjustments, but I’d stay away from dodging and burning in particular. At least in the version I have, there’s no undo feature, so an erroneous burn can wipe out what you’ve done, just like in a wet darkroom!
  7. You’ve now done pretty much all you can do in 32-bit mode, so set Upon Apply Convert To to 16 bpc. This will return a 16-bit image back to PS and change PS to 16-bit RGB mode. It’s also better to change to 16-bit mode while you’re still in 32 Float since there can be some rather quirky artifacts when the 32-to-16 bit conversion is done within PS.
  8. Back in PS, decide whether you want to merge in any of the original exposures. I will often do this in cases where there are ghosts such as people in different positions or if there are artifacts, details, tones or colors that are much better in one of the original images than in the merged one. If so, go back to LR, select the original RAW images and click on PhotoEdit In…Open as Layers in Photoshop… Back in PS, select the merged image then use Layer…Duplicate Layer to copy it as the top layer in the RAW-image stack. Use layer masking and other tools to manually combine your  originals and the merged image.
  9. Further tweak the combined image as necessary. If you need a filter that’s only available in 8-bit RGB mode such as Pixel Bender, Distort or the Topaz Labs suite, change the Mode to 8-bit RGB, but do so as late as possible. Otherwise keep the image in 16-bit mode.
  10. Click Save, which returns the image to LR.
  11. In LR do your cropping, final sharpening, noise reduction and vignetting.

Workflow #2: HDR Expose (without Photoshop)

This variation is designed for those who either don’t have PS or just prefer to do all their retouching in LR.

  1. Don’t make any adjustments in LR’s Develop module. The one exception might be if you need to correct for severe chromatic aberration, which is quite difficult to do later in the workflow.
  2. Select the bracketed RAW files in LR then select File…Export…Merge and Edit in HDR Expose. This uses HDR Expose’s alignment and merge engines instead of PS’s. Important: Make sure you select Merge and Edit Original Image(s) in the Export dialog box. This will send your RAW files directly to HDR Expose. If you select Merge and Edit Images with Lightroom Adjustment(s) you will be sending LDR 16-bit TIFF files and thereby throwing away a lot of important data. The only time to use this option is if you corrected chromatic aberration in step #1. It’s a tradeoff. [There’s a workaround for this tradeoff: You can make adjustments in LR’s Develop module. (I’d suggest limiting them to lens correction and camera calibration.) Then Export your set of bracketed RAW images as DNG files. This retains their full 32-bit range. You can then start HDR Expose as a standalone application and merge the saved DNG files.]
  3. Tonemap and adjust the image in HDR Expose.
  4. Click OK and save the image as a 16-bit TIFF. It will be returned to LR.
  5. You have the option at this stage to perform additional processing on the merged LDR image in PS. Use Edit in…Photoshop CS5 to export to PS. When you’re done, Save will return the results to LR.
  6. Crop, sharpen, reduce noise and vignette in LR.
  7. Continue with step 8 in Workflow #1.
Workflow #3: LR/Enfuse

Before a friend told me about HDR Expose and 32 Float, this was my first choice for HDR merging and tonemapping. Not only is it free (donationware, actually) it’s also fast and simple and produces a fairly linear tonemapped image ready for additional adjustment. LR/Enfuse is the open-source Enfuse command-line utility packaged as a LR plugin.

  1. Select your bracketed RAW images in LR.
  2. In the LR menu, select File…Plug-in Extras…Blend exposures using LR/Enfuse…
  3. In the Output tab select 16-bit ProPhoto TIFF and Reimport image into Lightroom.
  4. LR/Enfuse will perform the HDR merge and tonemapping. Although you can make some adjustments before it runs, there’s no interactive preview.

The tonemapping in 32 Float, HDR Expose and LR/Enfuse generally give me the most realistic results. But occasionally I want a less-realistic look, in which case I typically turn to Photomatix Pro. There are three different ways to use this utility, depending on the balance you want to strike between simplicity/speed and quality/control.

Workflow #4: Photomatix Tone Mapping Plugin for Photoshop

This plugin is sold separately by HDRsoft. It’s the best way to use Photomatix Pro with PS.

  1. Follow steps 1-4 in Workflow #1.
  2. Launch the Photomatix plugin by selecting Filter…Photomatix…Tone Mapping…
  3. In Photomatix tonemap the HDR image to LDR and make other adjustments. I tend to use default settings here, waiting until I return to PS to make further changes.
  4. Click OK, which returns a 32-bit HDR image to PS.
  5. Don’t worry if the LDR preview of the 32-bit HDR image looks all wrong in PS. Click on Image…Mode…16-Bits/Channel.
  6. If you want the double-tonemapping look, you can make further tweaks in this second HDR Toning step.
  7. Continue with step 8 in Workflow #1.
Workflow #5: Photomatix Pro (with Photoshop but without the Plugin)

If you want to work with PS but don’t want to buy the Photomatix Tone Mapping Plugin for Photoshop, this variation works fine. It’s just a little more complex.

  1. Follow steps 1-4 in Workflow #1.
  2. Save the HDR image as a Radiance (.hdr) file in a temporary location. (You don’t need to keep this for archival purposes since it is easily reproduced from the RAW images at any time.)
  3. Start Photomatix Pro and open the .hdr file.
  4. Use tonemapping and other adjustments to create an LDR image from the HDR image.
  5. Save the LDR file as a 16-bit TIFF and Import (Copy) it into LR. Use a filename that will place it near your originals in the LR grid view.
  6. If you need to make PS adjustments, use Edit In…Photoshop CS5, and return the results to LR as another LDR 16-bit TIFF.
  7. Continue with step 8 in Workflow #1.

Workflow #6: Photomatix Pro (without Photoshop)

This workflow bypasses PS altogether, moving images from LR directly to/from Photomatix Pro. This process is fine for some HDR images, but it has certain weaknesses. First, it depends on Photomatix Pro to perform the HDR merge and image alignment — functions performed better by PS.

  1. Select the bracketed RAW files in LR then select File…Export…Photomatix Pro. But make sure you change the File Settings in the Export One File dialog box to DNG. If you don’t do this, you’ll be sending LDR images to Photomatix Pro and therefore losing highlight and shadow detail. (For an in-depth explanation, see Are You Wasting Dynamic Range?)
  2. Photomatix Pro will merge the DNG (RAW) files into an HDR image.
  3. In Photomatix Pro use tonemapping and other adjustments to create an LDR image from the HDR image.
  4. Click on Save and Re-Import and Photomatix Pro will return a 16-bit TIFF to LR.
Workflow #7: HDR Efex Pro

Nik Software’s HDR Efex Pro is the new kid on the block. While I like Nik’s control-point UI and have settled on their Silver Efex Pro as the #1 plugin for monochrome, HDR Efex Pro has become a tool I don’t use much any more. But many people use it, so I’ve included it in my workflows.

  1. Follow steps 1-4 in Workflow #1.
  2. In PS select Filter…Nik Software…HDR Efex Pro. 
  3. After tonemapping and possibly making other adjustments in HDR Efex Pro click OK, which returns a 16-bit LDR image to PS.
  4. Continue with step 8 in Workflow #1.
Single-Image HDR

When your source is just a single RAW file, there’s no need for the Merge to HDR Pro step. In fact, you can’t run Merge to HDR Pro with just one image. In this case you need to get your RAW file to your tonemapping utility as directly as possible. Starting in LR, use one of these tools, ranked in order of my personal preference:

  • LR/Enfuse: Because it’s simple, this is a workflow I sometimes use for single-image HDR. Just follow the same steps described for Workflow #3.
  • Photomatix Pro: You can’t send a single RAW image through PS to the Photomatix Tone Mapping Plugin, but you can export a single RAW image directly to Photomatix Pro, which automatically returns the resulting image to LR. Use File…Export…Photomatix Pro, but make sure you change the File Settings in the Export One File dialog box to DNG as described in Workflow #6 for multiple source images using Photomatix Pro.
  • HDR Expose: This workflow is more cumbersome than using LR/Enfuse or Photomatix Pro, but it’s the process I use for single-image HDR if I’m not satisfied with the results from the simpler tools. HDR Expose is the standalone version of 32 Float, and it can open one or more RAW files directly. Unfortunately it can’t deal with a single image exported from LR, so you need to start HDR Expose and open the file from there. This means you’ll have to save the output of HDR Expose as a file (typically a 16-bit TIFF) then import that back into LR.
  • 32 Float: Because PS’s Merge to HDR Pro won’t accept a single RAW image, the only way to get the full dynamic range of a single RAW image into PS is via the extended-EV TIFF method, described below.
  • HDR Efex Pro: This application does not include a RAW file processor. The only way I know to preserve the full dynamic range of a single RAW file for HDR Efex Pro is to use the extended-EV TIFF method.
The Extended-EV TIFF Method

This is a method for recovering data from RAW files when the tools you’re using cannot read those RAW files directly. It is not required or recommended for any of the multi-image workflows above. The only time I use it is when I want to process a single RAW file using 32 Float or HDR Efex Pro, which is now pretty much never. You’re probably better off just using another tool such as LR/Enfuse, Photomatix Pro or  HDR Expose, but if you don’t have one of those applications or plugins, the following is your best choice.

I first learned this technique from Klaus Herrmann in the section in his online HDR Cookbook entitled Creating HDR Images the Right Way. (Look for the Five TIFFs method.) A RAW file can contain image data from the darkest shadow detail to the brightest highlights, spanning a range of 10EV-12EV. But an LDR file such as a 16-bit TIFF can only represent 6EV-8EV. The idea of the extended-EV TIFF method is to replicate the wide dynamic range of data found in a RAW/HDR image using a bracketed set of LDR TIFFs from that image. Each TIFF file will contain the data from a different (but overlapping) portion of the RAW image’s brightness range.

  1. Open the RAW image in a RAW file processor application such as Lightroom, Adobe Camera Raw (Photoshop), Phase One’s Capture One Pro, Nikon’Capture NX2, etc.
  2. Using the app’s Exposure slider or equivalent, reduce the luminosity by 4EV.
  3. Save the image as a 16-bit TIFF, preferably in the ProPhoto RGB colorspace, with a filename that both identifies the original image as well as the adjusted EV. Something like “IMG1234_-4ev”.
  4. Repeat the previous two steps so you end up with five TIFFs, one each with exposure adjustments of -4EV, -2EV, 0EV, +2EV and +4EV.
  5. Check the +2EV and +4EV images and decide if they should be included in the set. While the -4EV and -2EV are very likely to include extra highlight data that appears blown out in the 0EV image, the same is often not true for shadow recovery. If the +2EV and +4EV images don’t contain true shadow detail that doesn’t appear in the next-lower-EV image, don’t use them — they won’t add detail to the shadows, but they will increase the noise.
  6. Treat these three, four or five images as bracketed originals and submit them as input to your HDR merge application such as HDR Pro (Photoshop), HDR Expose, Photomatix Pro and HDR Efex Pro. You can see the results of my tests of this method at HDR Tools Comparison.

If you’re working with multiple bracketed RAW originals and you’re still getting blown-out highlights when tonemapping, you may be able to recover them using a variation of the extended-EV TIFF method:

  1. Create a 16-bit ProPhoto RGB TIFF with no exposure adjustment from each RAW original.
  2. From the darkest (lowest-EV) RAW image, create two additional TIFF files: one darkened an extra -2EV and another at -4EV.
  3. If you started with three RAW images, for example, you’ll now have five TIFFs.
  4. Use these TIFFs instead of the RAW files as the source images for your HDR merge process.
  5. As with the single-RAW image variation, you can also try +2EV and +4EV TIFFs made from the brightest RAW image, but again to avoid noise don’t use them unless they provide details in the shadows that don’t already appear in a lower-EV image.

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