Difference compares the colors of the blending layer and the base layer, then keeps the difference between them. The result can dramatically change the colors, producing high-contrast, inverted, and often surreal effects.
The Math
For each RGB channel, Difference subtracts one layer’s value from the other and uses the absolute value of the result. This means it doesn’t matter which layer has the higher value—the result is always the positive difference between them.
Mathier Math
The basic operation is:
Result = |Base − Blend|
For example, if the base value is 0.7 and the blend value is 0.3:
|0.7 − 0.3| = 0.4
If we reverse the values:
|0.3 − 0.7| = 0.4
The result is the same either way. That’s what makes Difference useful for comparing layers.
Core Rules of Difference
Black does nothing: Pure black has a value of zero, so the difference between the base color and zero is the original base color.
White inverts: Pure white has the maximum value, so comparing it with the base produces the inverse of the base color.
Identical colors become black: When the two layers have exactly the same value, the difference is zero, producing black.
Layer order doesn’t matter: Because Difference uses the absolute value of the difference, swapping the top and bottom layers produces the same result.
When to Use It
Checking alignment: Place a duplicate of your line art or sketch over the original. Areas that match exactly turn black, while differences become visible, making it easy to spot shifts or misalignment.
Special effects: Use Difference to create unusual color inversions, high-contrast effects, and surreal or glitchy color treatments.