Digital SLR cameras’ dynamic range–their ability to capture image data from light to dark–is improving all the time, but cameras will always be limited by lens mechanics. Since a camera lens can use only one aperture (lens opening size) per shot, it typically chooses the best compromise between dark and light throughout the frame, and in doing so it may not capture details in shadows or in bright areas of the frame. Even capturing images in RAW format can’t overcome this limitation. The only solution thus far has been to layer several exposure-bracketed images, taken by a camera mounted on a tripod to minimize ghosting or blurring, and then use editing tools to select the best-exposed parts of each image and blend them into one “high-dynamic-range” image. Many applications, including Adobe Photoshop Pro CS5 and Corel PaintShop Pro X4, support HDR image editing; even the iPhone 4 offers a form of HDR.
HDR Expose 2 provides much more control over HDR processing than either Photoshop or PaintShop Pro does, though. It supports 32-bit color, which Photoshop also supports, but Photoshop allows adjustments only in 8-bit or 16-bit color mode. HDR Expose 2 is a stand-alone application, but it comes with plug-ins for Adobe LightRoom and Apple Aperture. Unified Color sells a related product, 32 Float v2, which functions as a Photoshop plug-in.
Capturing HDR Images
To start, you instruct HDR Expose 2 to import images; it imposes no limit on the number of photos, but I found little benefit in adding more than four or five shots; usually, relying on my SLR’s exposure-bracketing feature to capture just three images worked adequately. On my four-year-old dual-Xeon workstation, the application required about 30 seconds to process three source images and show me a preview. I captured the images with aperture-priority, since maintaining constant aperture reduces the likelihood of alignment problems in the composition.
Trying to fill shadows by shooting and then combining far-too-overexposed shots usually resulted in very noisy images. While HDR Expose 2 has some noise-reduction functionality, applying enough of it to solve the problem typically made the image blurry (as is the case with the noise-reduction features in most editing applications). I found that the better approach was to process images that weren’t too extreme, and then use HDR Expose 2’s extensive tone-mapping features to brighten shadows.
When you import photos, the application asks you to choose a method for reducing ghosting artifacts, but once you make a selection and begin merging images, you can’t go back and choose another method without starting over. And once your images are merged and HDR Expose 2 shows your composition, you can’t remove any shots from the composition–say, if you decide that one of your images is introducing too much noise. Photoshop’s HDR tool does allow you to remove shots if you want.
Unified Color says that a new feature in HDR Expose 2, real-time processing, allows the application to render immediately, rather than after every change, thereby eliminating the lag time of the previous version. The application was still a little sluggish on my system, sometimes taking a second or two to process an update, but the company claims that most systems should not see any lag. HDR Expose 2 is OpenCL-aware, which means that it will use OpenCL-supporting graphics cards to assist in rendering.
Tons of Tweaks
HDR Expose 2 has an automatic mode, but I found that it rarely gave me what I wanted, so I used the program’s many manual settings instead. At the most basic level, you can set overall exposure and adjust both highlights output and shadows output. Keeping an eye on the application’s histogram window is very helpful, because nearly every adjustment affects the histogram. It can tell you, for example, whether the adjustment you just made obscured some of the image data in shadows. It also has buttons to toggle the display of blown-out highlights and blown-out shadows, plus a button that plays a sort of video that starts with your darkest exposure and ends with the lightest.
On top of that, HDR Expose 2 offers per-channel color adjustments, white-balance adjustments, and tone curves, and it has a somewhat unique feature that permits you to use a color picker to select a specific color in your picture (while keeping an eye on the live pointer in the histogram to ensure that you’re picking a visible color) and then adjust the exposure of only that one color to make it pop out.
You can adjust overall image contrast and a linked “local contrast,” which functions as a sort of sharpness command; I found that the latter worked well to sharpen tree leaves, which often appear fuzzy or ghosted in HDR images.
HDR Expose 2 does not allow you to create selections or masks. It does have a new dodge and burn tool, which lets you lighten or darken areas with a paintbrush, but without the ability to set boundaries with a selection, it seems crude to me–I couldn’t, for example, use its round brush in areas with square boxes, such as a rectangular sign.
High Dynamic Range, Low Price
Creating really good high-dynamic-range requires more than just good software; it requires you to take great care in choosing your shots, setting up your camera, and capturing your images. Once you get your process down, HDR Expose 2 will reward your efforts by helping you to produce stunning images. I’d prefer that it have some basic selection or masking features, but it’s still a very useful utility at a good price.