Blend Modes in Photoshop are simple at a glance, but it’s easy to forget exactly how each of the 27 modes work. This 10-minute video from Blake Rudis of f64 Academy goes in to detail on Luminosity and Color, which are both very useful for photo editing.
At some point, we’ve all been guilty of just cycling through blend modes in Photoshop to find the right effect. While it’s an effective strategy, it will dramatically improve your workflow to better understand what the blend modes do and when to use them.
This is how Adobe describes the Color and Luminosity blend modes, which are actually complete opposites of each other:
Color: Creates a result color with the luminance of the base color and the hue and saturation of the blend color.
Luminosity: Creates a result color with the hue and saturation of the base color and the luminance of the blend color.
From the description, it’s not easy to imagine the effect that the blend modes will have. The video at the top clears up any confusion by showing how they can be used to apply Curve or Gradient Map adjustments to the tones and colors of an image individually.
As an example, here are is an image with the blacks dramatically clipped with a Curves adjustment in order to best show the effect. The top half has the Curves adjustment set to the Normal blend mode. You can see that it dulls both the colors and the black tones. The bottom half of the image is the exact same adjustment, but set to the Luminosity blend mode. In this case, the colors remain the same as they were in the underlying layer.
The next image uses the same Curves adjustment layer, but this time the bottom is set to the Color blend mode. You can see that the adjustment layer has no affect on the blacks, which remain dark. The colors are affected, becoming almost completely grey.
Blake Rudis explains that he would usually use a Gradient Map with the Color Blend Mode applied, so that it adjusts the colors in the image without changing the luminance. Curve adjustments affect the colors in an image along with the tones, so he uses the Luminosity Blend Mode in this case to target only the tones.
Take a look at the video for a full and detailed explanation, and afterwards you may like to have a look at an earlier post here in PetaPixel, which delves in to all 27 blend modes in a 40-minute guide.