What’s the Difference with the Difference Blend Mode?
Over the last several years I have explored many of the blend modes in Photoshop for color grading, but I haven’t touched on the Difference Blend Mode. A lot of what happens here on f.64 Academy is psycho targeted experimentation and that stuff takes time, a lot of time! When someone says, “Hey Blake, can you explore x topic”, I do. I explore it a lot, sometimes I explore it for months. The Difference Blend Mode was one of those instances.
Taken from the Adobe Help Blog
Difference Looks at the color information in each channel and subtracts either the blend color from the base color or the base color from the blend color, depending on which has the greater brightness value. Blending with white inverts the base color values; blending with black produces no change.
I have traditionally used the Difference Blend Mode in the past for aligning layers. As the description implies, the difference blend mode subtracts the pixels of the base and blend layers and the result is the greater brightness value. Well, when you subtract two pixels with the same value, the result is black. This makes it very easy to see where images are aligned in Photoshop. If the resulting image (or most of it) is black, then you know the alignment is good!
I have stumbled upon a new way to use the Difference blend mode. This blend mode can be phenomenal for color grading. The idea is to use a solid color fill set to Difference. It will apply the color to the dark areas of your photo and automatically invert the color and apply it to the highlight areas. The result is a harmonious color grade that uses the complementary color principles of Color Theory to create a natural color grade.
Don’t be fooled, it is not as simple as it sounds. the Difference Blend Mode can be slightly unpredictable. You have to be thinking in terms of opposites at all times! If you use red, the primary color grade will be cyan. If that red has a bright value it will make the image darker, and if it has a dark value the result will be less in the highlights and more in the shadows. I suggest relying on pattern recognition and really experimenting.
The biggest take away here is that the Difference Blend Mode relies heavily on the FILL slider. Fill will act as the calculation of the math that happens within the blend mode and Opacity controls the intensity of that calculation.
To make it easier, I have made a video and a series of actions to assist you in your understanding of the Difference Blend Mode.