High-dynamic-range (HDR) imaging is a growing trend among photography enthusiasts. And Unified Color Technologies' latest software, HDR Expose ($150, price as of 8/5/2010), does a good job of providing new tools to increase your control over how your merged HDR pictures will look. But its interface impedes the editing process.

For the uninitiated, HDR imaging involves using a combination of images at different exposures to go beyond what a digital camera can capture in a single image. The human eye, in combination with the mind, can see and understand an amazingly wide range of color, light, and shadow--far beyond what even a top-of-the-line, professional digital camera can capture. That's part of the reason behind the popularity of HDR software, which is designed to boost a picture's gamut. This is done by combining the shadows from underexposed images, the midtones from well-exposed photos of the same scene, and the highlights from the overexposed version(s). Sometimes, the results can be very effective.

HDR Expose, which replaces the company's HDR PhotoStudio, is a 32-bit color editor that uses the company's wide-gamut Beyond RGB color model based on brightness, chroma, and hue (Bch). This allows the software to separate dynamic range from color information, so that when you edit the midtones, highlights, and shadows of a picture, you won't alter the colors, and vice versa. Another factor that sets it apart from other HDR editors is that all the color and exposure tools utilize the full 32-bit range.

HDR Expose's interface is quite different from its predecessor's, with a larger preview, plus the ability to have multiple merged images open in various tabs. All edits are now nested to the right of the screen, with each one added to a list, in the order you execute them. You can go back and adjust or remove any editing step in the list.

The simplicity of this design is appealing and helps organize the workflow. However, since the edits are cumulative, when you go to an earlier step to change the settings, you can preview the result based only on that step and the ones that preceded it. For instance, suppose you have a list of edits in this order: Brightness/Contrast, White Balance, Shadow/Highlight, and Saturation. When you go back to adjust the White Balance, your preview does not reflect any of the settings you've already established for Shadow/Highlight or Saturation.

The result of this discrete progression is a time-consuming, sometimes frustrating workflow of going back and forth among the dialogs to find the precise balance of settings for all your steps, to get the exact picture you want. What's more, the previews lag behind the edits, so that even the slightest change initiates an update progress bar, and while it's going on, you can't do anything but watch and wait.

Another problem is that there's no dedicated Undo command. So if you make an adjustment you don't like, to go back to the previous state, you have to remember just where the settings were. Happily, any list can be saved as a "recipe." However, even if you save your merged file using Expose's BEF file format, its history (or list of edits) is not retained, so the edits that defined the merge can't be adjusted. (United Color Technologies says that they are revisiting this and that the file may retain the edit history in the future.)

One of the problems with HDR images is that they usually have a wider range of highlights and shadows than can be reproduced in print, which has, by its nature a more limited gamut. In HDR Expose, the new Histogram Screen Zone allows you to see how much of your image data will be printable, and you can adjust your edits accordingly. In addition, an eyedropper provides point values in the picture for both RGB and Bch.

An HDR image is created by combining several exposures of the same scene, which means that there can be elements, such as waves or a moving car, that may change position from one exposure to the next. So, when the images are combined, you can end up with ghost-like objects having blurred or double-exposure edges. HDR Expose does an excellent job of eliminating such ghostly artifacts. The new ghost reduction tool offers three choices: Natural (handles larger view movement, such as waves or clouds), Sharp (for moving objects, such as cars and people), and Smooth (which combines both options). When we used Smooth on a wind-blown leafy twig growing out of a dark tree stump, we ended up with no ghosts whatever.

We compared HDR Expose with Photoshop CS 5's HDR Merge tool, using the same test images. Without question, HDR Expose produced a much sharper, cleaner image, with far better details. However, Photoshop's midtones were more natural and less contrasty. HDR Expose has many more controls within the 32-bit merge environment, which means that we might have eventually ended up with just as nice midtones as in Photoshop. But the great complexity of options in HDR Expose, which gives a user a high degree of control, can also mean that it might take much longer to get the results you need and want. (Incidentally, the Photoshop HDR Merge also gave us good ghost-free results on the leafy twig merge mentioned above.)

HDR Expose works with many, but not all RAW file formats. For instance, it currently doesn't support Samsung's SRW file format. However, it does ship with a plug-in for Lightroom and Aperture. So you can use Lightroom or Aperture to do the RAW conversion, while using HDR Expose's 32-bit environment to handle the merge, as well as much of the global color and exposure issues.

HDR Expose is a very good program that produces sharp, clean, attractive, high-dynamic images, though its midtones tend to be overly contrasty. Our biggest complaint is that, even with an interface redesigned from the earlier HDR PhotoStudio, the workflow can be clumsy and time-consuming.