Most documentation on Photoshop Blend Modes stinks. That's why most users rely on trial and error in order to achieve the effect they want. Here's to a better understanding of what the blend modes do, and when to use them:Some of the blend modes are designed to make life easier for artists who wish to hand color comic books and storyboards by placing flatly-colored cartoony artwork in one layer, and highlights and shadows in another layer.
Highlights are usually screened over a drawing.
Shading is usually multiplied into a drawing.
Overlay is a blend mode which combines the multiply blend mode with the screen blend mode. It does so by looking at the image under the artwork. Where the image under the artwork has pixel values less than "middle gray" (127 in 8-bit space) the two layers are multiplied. Where the image under the artwork exceeds middle gray, the two layers are screened.
Oddly enough, Hard Light does the exact same thing. The only difference between the two is that Overlay likes the artwork in the upper layer and the modifications to the artwork in the lower layer, while Hard Light likes it the other way around. In the diagrams above and below, a (overlay) b and b (hard light) a produce identical results.
Here is the Hard Light blend mode in action again on another example.
For comparison, I've thrown in some of the other blend modes using the same source images. Pay close attention to the order of the layering in each of the operations detailed below.Soft Light is similar to Hard Light in that it combines two other blend modes. In this case, instead of multiply and screen, burn and dodge are used. The results are somewhat similar.
Vivid Light:
Vivid light favors the light values but doesn't pick up as much on the dark values.
Linear Light:
Notice how linear light picks up the dark colors more. You can really see it in the gold plates.
It's easy to make interesting lighting effects on curved surfaces. The hard part is lighting the boring flat front faces of reflective metal letterforms. Blend modes like vivid light and linear light are especially useful for creating punchy animated sheens on metallic flying logos.
Pin Light: Although I included it for comparison, this example shows off the pin light blend mode to poor effect. Pin Light is really a "lazy" combination of the lighten and darken blend modes. If you paint with a color above middle gray, Pin Light assumes you wish to lighten. If you paint with a color darker than middle gray, Pin Light assumes you wish to darken.
