Double-Process RAW For Better Tonality
Don't try to do it all in one step. Use the power of RAW to process two separate images optimized for different tonalities.
The image shown here is from the wonderful light show at Chicago O'Hare International Airport in the tunnels between terminals. I had a four-hour layover at the airport, and being a photographer, I appreciated the neon lights that played around the moving walkway that connects the different concourses, so I decided to photograph them. I rode back and forth on the walkway, shooting many different exposures at many different shutter speeds.
That's one great thing about digital—using the image review on the LCD, I could check the shots and look for such things as the highlight warning to make sure I wasn't overexposing the bright highlights. I placed the highlights just on the verge of overexposing so that I could keep the overall photo bright while still retaining detail in the highlights.
When I returned home, I processed the image in Adobe Camera Raw, built into Photoshop CS2. Photoshop CS2 is the first version of Photoshop that allows you to open two copies of a file with the same name, which makes this technique easier. Otherwise, when you first open a processed file, you have to rename it before you can open a newly processed image from the same file.
(STEP 1) Process For Highlights. The first time I processed the image, I moved Exposure down to a minus number to bring the overall exposure down about a half-stop. I watched the bright colors to make sure I held all the detail and color in the brightest areas of the picture. The darkest parts of the photo are unimportant at this point. I opened this version into Photoshop.
(STEP 2) Process For Shadows. I went back into Camera Raw and processed the image a second time. This time, I opened up the shadows by moving the Shadow slider to the left (which reduces its setting) and by adjusting the Exposure slider to the right. This processing step is purely about the dark areas, so having the bright colors lose detail didn't matter. You may find, as I did, that when the shadows are opened up like this, they appear a bit flat. I added a little contrast to the image because of that. I also opened this version into Photoshop.
(STEP 3) Create A Layered Image. Now you bring the two processed images together into one file. Since they come from identical files, they will match exactly. I put both images side by side in Photoshop. Using the Move tool and holding down the Shift key, I clicked on the lighter image and dragged it in perfect registration onto the darker image (the Shift key keeps them aligned). You must move your cursor completely onto the second photo or you'll get an error message that says you can't move the background layer.
The result is a file with two pixel layers, the light image over the darker image. You'll find that some photos do better with the darker image over the lighter image. There's no absolute rule for this, though often it's best to put the image needing the least amount of work on top.