Blend Modes allow you to achieve a lot of subtle visual effects. I find that their greatest value is in making an image feel coherent. Things feel as if they are actually drawn on the parchment, for instance.

A layer’s (or a layer style effect’s) blend mode changes how the rendered pixels of the layer behave based on the rendered pixels beneath it. There are many modes, each of them with different math, and a full reckoning is beyond this short (hah!) tutorial. However, there are a handful of modes that you’ll use more often than others and which one you choose often depends on how “dark” the current layer is.

You’ll find a lot of happy accidents with blend modes, by the way. Experimenting with them is a great way to find new things and to learn how each mode behaves. I highly recommend it.

You can edit a layer’s blend mode from either the Layers tab or through the Layer Effects dialog. Note that blend modes do not reset when you turn off Layer Effects.

Basic Blend Modes

Here are some basic blend mode types.

• Normal. Show the rendered pixels of this layer exactly as they are.
• Overlay. Allow the layers below to “ghost” through. This is good for most layers of medium darkness. Does not work well if the lower layers are darker.
• Screen. Applies the layer in a “lightened” fashion (the “Lighten” mode also does this, but in a slightly different way). Use when your layer is light-colored overtop a medium or dark-colored layer.
• Multiply. Darkens or burns the layer into those below it (the “Darken” mode also does this but in a slightly different way). Use this when your layer is darker than the ones below it. It’s useless against a dark layer.
• Color. Applies the color of the layer to the ones below, subtly changing them to match. This is best used when the entire layer is a single color, or as a layer effect (Color Overlay with mode set to “color”).
• Color Burn. “Burns” the color of the layer to the ones below, overall darkening the layer but enhancing parts of its color profile.
• Color Dodge. “Dodges” the color of the layer to the ones below, overall lightning the layer and de-emphasizing parts of its color profile.
• Linear Light. Applies the pixels in a more black-and-white, high-contrast way. Lighter colors (especially white) tend to disappear. This one is super-useful for adding texture and noise.

Here is the same black-and-white image (an illustration showing convergent evolution) applied over a texture pattern in various blend modes:

As you can see, the various modes can have significant effects. The Soft Light mode is probably what you’d want to use if you wanted to make a parchment version of this image feel coherent. I love the effect of Difference but that probably won’t work very well. However, Divide may work very well, especially if the opacity is lowered.

Here is how the same patterns and shapes appear on a parchment background in various modes. The circles are just colored circles; the little icon is a simple but meaningless set of brush lines.

Blend modes can be applied to layer groups as well. When doing so, the entire group is affected as if it were merged. Groups have an additional mode, Pass Through, which means “don’t do anything funky at all”. Setting a layer group to Normal has the effect of “crunching” everything and canceling any effects it overlays. You’ll hate it; don’t use it.

Additionally, you can apply blend modes to various layer style effects. This will change how they display. The example below shows how applying a Pattern Overlay effect changes depending on the blend mode of its application and the color of the shape it’s being applied to.