Shadow/Highlight inside Photoshop CS part 1
The Shadow/Highlight function, I’m told, comes to use via the same engineering team that developed the Healing Bush tool that debuted in Photoshop 7. It is, of course, a completely different tool. But what it has in common with the Healing Brush is the way it performs complex image manipulations under the hood and provides you with a simple front end for getting the job done quickly. To give you an idea of how this works, take a look at the image below. This is the original image (from a clipart collection), showing a mountain range in silhouette.
But what if I don’t want it to be in silhouette? What if I want to bring out the details on the mountain and the foreground from this excessively dark photograph? No problem.
How’d I do that? Well, I just selected Image > Adjustments > Shadow/Highlight, and cranked up the “Shadow” value to 100 percent.
And that’s literally all there was to it. It sucked out the data that existed in the file (despite resizing and multiple JPEG compressions) and composited it into the original in real time as I adjusted the slider, similar to much more painstaking processes that probably wouldn’t yield results nearly as satisfactory.
But Shadow/Highlight is not just about shadows. It’s an image adjustment function designed to accentuate the details in highlights as well. So here’s the same image with a 77 percent Highlight adjustment to provide a little definition in the clouds. (Note the differences in the cloud formation on the right.)
Not too bad? Well, of course, I don’t want to give you the idea that this is some kind of magical image manipulation tool. If there’s detail in your photograph, Shadow/Highlight can find and accentuate it. But in images that are too overexposed, detail can be permanently lost. To a lesser degree, the same goes for images that are too underexposed. In cases where your lighting simply doesn’t allow for exposures that capture data in the extremes of light and dark, you’ll still be better off bracketing your photos and then using something like the Blend Exposure filter from Reindeer Graphics’ Optipix suite.
But even with difficult images, Shadow/Highlight provides additional tools for finessing all the data out of your image.
Beyond its simple slider adjustments for Shadow and Highlight values, the Shadow/Highlight function also provides a wide variety of tools for fine-tuning your adjustments. You can access these by clicking on the “Show More Options” checkbox at the bottom of the dialog.
The Tonal Width settings allow you to to tighten or widen the range of tones that will be affected by your Shadow/Highlight adjustment. For example, you may want to bring out the details in t=only the darkest portions of your image, leaving some of the midrange elements alone, or you may want to brighten up more than just the darkest portions. The images below show examples of variations on the Tonal Width setting and their impact on neighboring tonal values.
Radius, on the other hand, does not target tonal values but instead allows you to adjust the area around each pixel in the adjustment. It’s a bit more obscure than Tonal Width, but it can have a dramatic impact on the final result of your manipulation. The images below show variations on Radius. (Each uses a Shadow and Tonal Width value of 100.)