Wednesday, May 15, 2013

Photoshop's 32-Bit Mode vs. HDR Efex Pro 2

HDR has typically involved tone mapping with its often garish or unnatural results. Then Photomatix offered Exposure Fusion that excelled at natural rendering, though it was not tone mapping or true HDR. Since then, tone mapping has improved at producing natural-looking images as demonstrated by the latest version of HDR Efex Pro 2. Now there's another viable option lurking within either Lightroom or Photoshop CS6.

When you lift the hood on Photoshop CS6, you’ll notice a new feature that changes the HDR equation. I’m not talking about Photoshop’s HDR Pro tone mapping, which frankly is not up to par with Photomatix or HDR Efex. Instead, it’s the ability to simply take multiple exposures and merge them into a 32-bit floating-point file that is editable in either Camera Raw or Lightroom. This means you don’t need separate HDR software and have to struggle with all their arcane controls; and best of all, it’s great at natural rendering. But now the $64 question: is it really better?

To answer that question, I processed several HDR images and compared them side-by-side on screen. Since the editing options are so varied between the two processes, each with their own unique advantages, I took a Machiavellian “ends justify the means” approach. In other words, I used whatever tools available in HDR Efex, Camera Raw, Color Efex Pro, and Photoshop to produce the best end-result for both processes. At the end, it's what looks best that counts and not how amazing the process was to get there.

How to generate a 32-Bit File
I’ll describe how to generate a 32-bit file based on my workflow environment using Adobe Bridge and Photoshop. In Bridge, I select the HDR images and click: Tools → Photoshop → Merge to HDR Pro. After processing in Photoshop, I set the Mode to 32 Bit and click OK. Except for optionally checking the deghost box, that's all you do. When the image opens in Photoshop, it won’t look anything special, but don’t worry. I then save the image as a TIFF file using the following TIFF settings (which should already be the default): 32 bit (Float), LZW (or None) compression, Interleaved, and IBM PC. Then close or exit Photoshop and return to Bridge. From Bridge, select the TIFF file and right-click: Open in Camera Raw. (Important: make sure in the Camera Raw Preference the JPEG and TIFF Handling option is not set to Disable TIFF Support.) [Update: In Photoshop CC you can skip the save file step. Instead, you now check the 'Complete Toning in Adobe Camera Raw' box and then click 'Tone in ACR'.]

Camera Raw is now your substitute for HDR tone-mapping software. It’s like editing a normal raw file, except one with enormous dynamic range. That means you’ll initially start with radical settings in the Basic Panel; specifically, near -100 for Highlights and +100 for Shadows, and very large values for Clarity. You can then proceed to use the rest of Camera Raw’s features to edit the image. When done, click Open Image or Open Object (depending on the default) and continue in Photoshop. Now you can use Photoshop, or as I did with my test samples, start first with Color Efex Pro and then fine-tune them in Photoshop.

For the sample image below, I selected a classic daytime high-contrast image with a bright and cloudy sky, a shaded cliff side, and day-lit foreground trees. Though you can’t judge a process based on one image, I think this image is somewhat representative of the general differences.

When I processed the 32-bit mode image, it took Camera Raw’s HSL/Grayscale Panel to improve the autumn tree colors to compete with HDR Efex Pro’s rendering. Furthermore, it took Photoshop’s Shadows/Highlights tool to improve the cloud rendering and deep-shadow detail to compete with HDR Efex Pro. In the end, it took a little more finessing in Camera Raw to even things up, but at least you’re using familiar tools and not dealing with the arcane tone-mapping controls in HDR software.

When you view the two images below, you’ll note a modest, but by no means dramatic, difference. Unfortunately, the differences may be difficult to observe in these low-res images, but they are more obvious when viewing the original file or a large print. Overall, HDR Efex retains the tone mapping advantage of extracting better detail and contrast within the highlights and shadows and better overall midtone contrast and color saturation. But the 32-bit mode is superior when it comes to noise suppression and—the bane of tone mapping—halo artifacts. I zeroed-out the Structure setting in HDR Efex and still couldn’t match the 32-bit mode’s near-zero noise in the blue sky. And though this HDR Efex example didn’t suffer from halo problems, when compared to other images that had halo problems, the 32-bit mode versions were immune.

There were other fundamental differences I noted with the other test photos. The 32-bit mode process doesn’t compress the tonal range as well as HDR Efex. Below is a portion of a photo of the Zion Watchman illuminated by the setting sun. HDR Efex better captures the detail and color saturation while the 32-bit mode tends to blowout the highlights with higher contrast. This illustrates not to go overboard with the Clarity slider, which tends to blowout the highlights. The deghost option in Photoshop’s HDR Pro was also not as effective as HDR Efex’s; but that said, try not to use either whenever possible. Finally, I noticed in a few samples where the 32-bit mode picked up some banding artifacts in the sky while HDR Efex was clean of that, but was still prone to its usual haloing tendency.

32-Bit Image
HDR Efex Pro Image
32-Bit Image
HDR Efex Pro Image

If you have either Lightroom or Photoshop CS6, I think you could comfortably survive using the 32-bit mode as your sole means to process HDR, especially if you don’t want to invest either the money or learning time in more software. However, given the new lower $149 price on the Nik Collection that includes HDR Efex and Color Efex (and other highly desirable plugins), cost and learning curve may not be a deterrent. In that case, with my philosophy to always extract the last drop of “fine” in fine-art photography, HDR Efex Pro will continue to be my first tool of choice. That said, the 32-bit mode is still an invaluable backup and now rivals Photomatix’s Exposure Fusion as my backup if HDR Efex Pro should ever go squirrely with a particular image. 

Besides landscape photography, there are many other photo subjects done with HDR that, by their nature, may possibly render better in 32-bit mode (or Photomatix for that matter). For example, though HDR Efex may have the advantage in tone mapping, Camera Raw (or Lightroom) has some 32-bit mode editing advantages. Specifically, the neutral-gradient density filter tool is superior to the one in HDR Efex Pro, and the ability to edit hue/luminance/saturation by color or set white balance is lacking in HDR Efex Pro. In the comparison photos above, note that I was able to emphasize the blue sky more in the 32-bit mode image. 

I have experienced times that when using HDR it can be highly unpredictable. That's why I recommend to always try to shoot a backup using a neutral-density gradient filter if possible. Lacking that, having multiple options to process HDR does relieve me of some anxiety when I do have to totally rely on HDR. So it's worthwhile to consider investing in more than one HDR process.

[Notice: If you have an older version of Photoshop, you no longer can upgrade to CS6 (this does not apply to Lightroom). CS6 has been replaced by Photoshop CC (Creative Cloud) and is available only through subscription. Visit the Adobe website for more info.]

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