Blending Modes

The blending model for a layer sets how the resulting pixels in that layer blend with the pixels of layers below it to create the resulting pixel in the final image (what you see on the screen). The default "Normal" blending mode merely takes the pixels of the current layer and replaces the pixels that were below.

The various blending modes can be divided into four basic categories: Darken, Lighten, Contrast, and Color modes. The Darken modes make the image. The Lighten modes make the image lighter. And the Contrast modes make the image darker where the current layer is darker than middle gray, or make the image lighter where the current layer is lighter than middle gray. The

Color modes cause the current layer to only change the Hue, Saturation, Color (Hue and Saturation), or Luminosity (density) of the image. (The Dissolve, Difference, and Exclusion modes are used mostly for special cases.)

To understand the blending modes, you need to think of a pixel for the top layer as having three basic components; the pixel combination of all the layers below the current layer, the pixel generated by the current layer, and the resulting pixel in the final image - the resulting pixel is the pixel that is actually displayed on the screen, and is passed on upwards to other layers.

The "Normal" blending mode is simple. The current layer merely replaces the pixel of the layers below the current layer.

Resulting pixel in final image

Pixel in current layer

Pixel below blending layer

Replace

Replace

Use luminosity

Multiply

Normal

Luminosity Multiply

A common blending mode is "Luminosity"; this mode takes the luminosity from pixels in the current layer and combines these with the color from the pixels below to create a new pixel; one with the old color combined with the new

luminosity. The other color blending modes behave similarly, changing only the hue, saturation, or color of the pixel.

This mode is especially useful if you want a layer to only change the luminosity (or density) of the image. It is common for adjustment layers that apply significant density changes to also result in some moderate color changes. A curves adjustment layer that adds a moderate amount of contrast can also result in a slight change in color - changing the blending mode of this curves adjustment layer forces the layer to only change the luminosity and not change the color.

The color blending modes can be used for most common adjustment layers that adjust brightness, contrast, color, or saturation. In general, a brightness or contrast layer should only change luminosity (so the blending mode should be set to luminosity); a color or saturation layer should only change color or saturation.

Another common blending mode is the "Multiply" mode - this mode takes the pixel in the current layer and "multiplies" it with the pixel below it (don't worry about the actually process of multiplying). The multiple mode results in a darker pixel than either of the original pixels. The opposite blending mode is "Screen" -this mode takes the pixel in the current layer and "multiplies" it with the inverse of the pixel below it. The screen mode results in a lighter pixel.

Multiply blending (darkens image)

Screen blending (lightens image)

Overlay blending (lightens and darkens)

Original layers

Multiply blending (darkens image)

Screen blending (lightens image)

Overlay blending (lightens and darkens)

Original layers

The Overlay blending mode is a compromise between lighten and darken; where the current layer is dark, the resulting image is darker; where the current layer is light, the resulting image is lighter.

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