Blend Modes
Layer Blend Modes
A layer's blend mode specifies how it is blended with the layers immediately below it in the layer stack. Changing the Blend Mode on a single layer can radically alter the composite of design.
To change a layer's Blend Mode, double-clicking the layer in the Layers Window.
Tool Blend Modes
In the dialog the Blend Mode drop down list offers 14 blend modes. Click one to apply the blend mode to the layer. The new blend mode will be applied to the entire layer. It is not possible to apply a layer blend mode to part of a layer.
The order of the layers in the layers stack is important when using layer blend modes. Layer A blended over Layer B is not the same as Layer B blended over Layer A - even if the same blend mode is used.
Select the blend from the list and use the tool as normal to have the blend mode applied as the tool covers the design. The tool and blend mode will be applied to the active layer as if the tool was being used on a new layer immediately above the active layer and the results merged down following the editing operation.
For the following explanation, these 2 images will be used to demonstrate the layer blend modes:
Background layer(left) and top layer(right)
Blend modes
Each pixel's RGB component intensity is multiplied with the pixel value from the composition. The result of this blend mode is always darker than the original. White pixels in the blend layer are effectively rendered transparent by the Multiply blend.
Each pixel's RGB component intensity is added to the intensity of the pixel values from the composition. The Additive blend has the effect of brightening pixels in the final composition. Black pixels in the blend layer will be rendered as transparent by the Additive blend.
This blend mode has the effect of making dark pixels darker while lighter pixels must be blended with other light colored pixels in order to remain bright.
This can be thought of as the opposite of Color Burn. Lighter pixels retain their brightness while darker pixels must be blended with other dark pixels in order to remain dark.
This blend mode can be used for adding shiny objects or areas of light. Black pixels in the blend layer are ignored as if they were transparent.
This is the reverse of the Reflect mode: it works the same as swapping the layer positions and using Reflect. Glow effectively brightens the composition by the amount of brightness in the blend layer. Black pixels in the blend layer are rendered as if they were transparent.
This is a combination of Screen and Multiply modes which uses the blend pixel intensity to determine the result. For darker colors, this acts like Multiply. For lighter colors, this acts like Screen.
The counterpart to Additive blending. The layer pixel's intensity is subtracted from the composition pixel's intensity resulting in darker colors.  Subtraction could produce a negative intensity which is unable to be displayed, so an absolute value is returned. Thus, both "white minus black" and "black minus white" will both produce white. Difference blend is often useful when using the Clouds effect.
At first glance this seems similar to Difference, however it actually produces the opposite effect. Instead of making colors darker, it will make them brighter.
The lightest pixel of either the blend layer or the composition is used.
The darkest pixel of either the blend layer or the composition is used.
This can be thought of as the opposite of the Multiply blend mode. It is used to make pixels brighter, with black being effectively transparent.
This is short for "exclusive OR", which is an advanced blending mode that is primarily used for image analysis. Pixels in the blend layer which exactly match the composition will be rendered black. Where differences exist, colors are shown.