Anyone who has dabbled in Photoshop has probably wondered at some time what the hell all the blending modes actually do. With this in mind I created the following swatches some time ago, to help me select the most appropriate modes for creating mockups of shading and lighting effects.

The samples here illustrate the result of blending the following two images (disregarding the color specific blends for now).

What I find striking about the results is that many of them have discontinuities, which seems a little crappy to me. Eg overlay and hard light, which both appear to be based on combinations of multiply and screen simply stuck together.

	Multiply: A*B
	Screen: 1-(1-A)*(1-B)
	Overlay: if (A<0.5) 2*A*B else 1-2*(1-A)*(1-B)
	Soft Light: ???
	Hard Light: if (B<0.5) 2*A*B else 1-(1-A)*2(1-B)
	Color Dodge: A/(1-B)
	Color Burn: 1-(1-A)/B
	Darken: min(A,B)
	Lighten: max(A,B)
	Difference: |A-B|
	Exclusion: 0.5-2*(A-0.5)*(B-0.5)