One of the most versatile and powerful secrets of Photoshop is the luminance mask. Similar to a channel mask that allows you to select very precise parts of your image based on color, the luminance mask allows you to select parts of your image based on tonal range. Using Photoshop to select those tonal ranges for you, you can quickly and effortlessly make very specific color and contrast adjustments to color grade like a pro.
This is not a tutorial on how to make huge adjustments to your image (although luminance masks certainly allow for that); this is a tutorial on how to subtlety color grade an image to give a result that doesn't look like a preset. The best part, though, is that it's almost just as easy.
- First, create the adjustment layers that you will be using to do your color grading. In this example, I've used a Photo Filter Adjustment Layer. One for the highlights and one for the shadows. Disable both adjustment layers for now.
- Second, select the mask of the highlights adjustment layer. Go to Image > Apply Image. Set the Layer to "Merged," set the Channel to "RGB" and set the Blending to "Multiply." Hit OK.
- Alt or Option+click on the mask to show only the mask. Use Levels (not a Levels Adjustment Layer) to change the contrast of the mask to select the proper range of the highlights.
- Adjust settings of the adjustment layer to taste.
- Repeat the steps for shadows, but during Apply Image, select "Invert."
The great thing here is that luminance masks can be used however you want. They can be used for contrast, color or virtually any other selective effects. Sharpen on the highlights? Sure. Remove noise from the shadows? Absolutely. When printing, it's common for the image to print darker than it appears on screen. Instead of brightening the entire image, I use this process to select the shadows to only brighten those tones, while preserving the tones of the rest of the image.
Good luck! Hopefully you find this as handy as I do!