Contrast determines the separation between the dark and light colors. This value works multiplicatively across many ColorCorrectionEffects’ Contrasts. Values less than 0 have reduced contrast, and values greater than 0 have increased contrast. By default, this value is 0 (no change). Only values in the range [-1, 1] will produce a change. Values outside of this range have undefined behavior.
Contrast of 0 vs 0.5:
Contrast of 0 vs -0.5: