LAYER BLENDING MODES

Technical Details

This tutorial was prepared by Roy Killen and is copyright. It is part of the training materials provided for members of the Belmont 16 Ft Photographic Club and is not intended as a complete, stand-alone instruction package.

Before reading this tutorial you should check the introductory tutorial on Layer Blending Modes.

Comments and suggestions on this tutorial are welcome - they should be emailed to Roy Killen.

THE LAYER BLEND MODES

There are 25 layer blend modes availablel in Photoshop CS3 (two new ones were added after CS2) and they are in six groups (with lines separating them on the pop-up list). Actually there are five other blend modes that do not appear on the layers blend mode pop-up menu - but that's a story for another tutorial.

Each blend mode provides a different way of altering the colour or luminosity of each pixel in an image depending on the colour or luminosity of the pixels in the blending layer and in the layer directly beneath it.

Changes to the blend mode of a layer do not physically alter any of the pixels in an image - so they can be reversed so long as you keep the layers in the file.

Note: When the Background layer is selected the blend mode options are greyed out - the Background layer blend mode cannot be changed (becasue there is nothing below it to sample).

The blend mode pop-up in the Layers palette looks like this:

For general photographic work, the blend modes that you will use most frequently are Normal, Multiply, Screen, Overlay, Soft Light and Luminosity. However, the other blend modes provide a wide range of ways in which images can be modified or enhanced.

The effects of many of the blend modes are based on the luminance of the pixels in the blendng layer (rather than on colour). So I will demonstrate some of these effects by blending an image (the background layer) with a layer that consists of two black-to-white gradients running in opposite directions.

Don't try to memorise the effects of all these different layer blending modes - it will drive you crazy. Instead, try to remember the general effects of each group of blend modes and then experiment with a range of different images so that you gradually get to understand which modes might produce the effect you are looking for in a particular type of image.

Bottom layer - original image

Top layer - blend mode will change on this layer

Blend mode: NORMAL

What you see is simply the top layer (assuming that the opacity is set to 100%).

In this example the opacity of the blend layer has been reduced to 70% so that you can "see through it" to reveal the bottom layer.

Blend mode: DISSOLVE

This mode takes the opacity of the blend layer (0-100%) and uses it as the percentage of pixels from the blend layer that will be visible. The remaining pixels are from the base layer.

In the example shown, the opacity of the blend layer is set at 20% so the result is an image consisting of a random selection of 20% of the pixels from the blend layer and 80% of the pixels from the base layer.

Notice that the pixels from the top layer that are visible (the "specks") are the colour and luminosity of the top layer, the rest of the pixels are the colour and luminosity of the bottom layer.

DARKEN BLENDING MODES (white neutral blend modes)

With this group of blending modes, white in the blendng layer has no effect on the underlying layer.

Any pixel darker that white has the potential to darken the underlying pixel.

Blend mode: DARKEN

This mode compares the brightness of the pixels in the blend layer and the pixels in the base layer - the darker of the two is chosen as the result.

When the base layer pixels are lighter than the blend layer they are replaced with the blend layer. (Top left and bottom right of the example.)

When the base layer pixels are darker than the blend layer the bottom image "shows through". (Top right and bottom left of the example.)

When the blend colour is white, it has no efect on the underlying layer. (That's why this group of blend modes is called "white neutral".)

This blending mode can be used to cover light portions of an image while letting the dark areas show through, which can be useful when retouching images.

NOTE: When the blending layer is coloured (rather than the greyscale image used in this example) Darken compares the red, green and blue channels of the two layers separately. The darkest colour components of each of the compared pixels are selected - and this can produce some unusual colour changes.

The opposite of this blend mode is LIGHTEN.

Blend mode: MULTIPLY

This mode multiplies the base colour by the blend colour and produces darker colours everywhere except where the pixels in either layer are white.

Multiplying any colour with black produces black. (Top left and bottom right of the example.)

Multiplying any colour with white leaves the colour unchanged. (Top right and bottom left of the example.)

Unlike most layer blend modes, this one has several "real world" equivalents. If you imagine that the two layers were both images on transparent slides - the Multiply blend mode produces the same effect as putting the two slides together and holding them up to the light. It also produces the same effect as printing the bottom layer with an inkjet printer and then feeding the paper through the printer again and printing the top (blending) layer.

Although the effect of Multiply is similar to the effect of Darken, Multiply produces smoother transitions and preserves more detail. You can see this across the centre of the example.

Blend mode: COLOUR BURN

This mode darkens and adds contrast to the original image.

The darker the blend colour the darker and more contrasty the result.

Black will leave any red, green or blue numbers that are 255 alone and force all others to zero (black). Notice this on the sign in the bottom right.

Blending with grey darkens and intensifies the colours in the underlying image (such as in the lower right of the sample image).

Blending with white produces no change.

Blend mode: LINEAR BURN

This mode acts a bit like Multiply but has a greater tendency to make areas pure black (such as in the top left of the sample image). It produces a more contrasty and more saturated result than Multiply.

The darker the blend colour the darker the overall result.

The effect is similar to Colour Burn, but whereas Colour Burn darkens the base colour by increasing contrast, Linear Burn darkens the base colour by decreasing the brightness.

Blending with white has no effect.

Blend mode: DARKER COLOUR

This is a new mode introduced with CS3.

It compares the total amount of light (sum of the red, green and blue values) in each pixel of the two images and uses the values from whichever pixel is darker.

The main difference between this and the Darker mode is that the Darker mode compares the individual colours in each pixel (not the total amount of light) and produces a colour that is different from either of the original two layers. You can see this most obviously in the green tinges that were introduced at the edges of the grey areas in the Darken example above).

Blending with white has no effect.

LIGHTEN BLENDING MODES (black neutral blend modes)

With this group of blending modes, black in the blendng layer has no effect on the underlying layer.

Any pixel lighter that black has the potential to lighten the underlying pixel.

Blend mode: LIGHTEN

In this mode, each of the corresponding pixels in the two layers is compared and the lighter of the two is used as the final result.

Because this mode looks at the red, green and blue components of each pixel separately it can produce some unusual colour shifts - such as near the middle of this example.

Blending with black has no effect because it will always be the darker of the two pixels being compared (as in the top left and bottom right of the example).

Blend mode: SCREEN

This mode has the opposite effect to the Multiply mode.

Black in the blend layer has no effect (it simply allows the underlying image to show through).

Any pixel lighter than black in the blend layer lightens the pixel beneath it.

The "real world" equivalent of Screen mode is the effect you would get by projecting the two images from different slide projectors onto the same screen.

Blend mode: COLOUR DODGE

This mode brightens the base layer according to the brightness of the blend layer and usually makes the colours more saturated.

Where the blend layer is near white the result will be "washed out" - as in the bottom left and top right of the example.

Black in the blend layer has no effect on the result.

It can be useful for simulating hot spots in an image.

Blend mode: LINEAR DODGE

This is similar to Colour Dodge but the result will have less contrast and less saturation - but more contrast and saturation than you get with Screen mode.

Black in the blend layer has no effect on the underlying layer.

Blend mode: LIGHTER COLOUR

This is a new mode introduced with CS3.

It compares the total amount of light (sum of the red, green and blue values) in each pixel of the two images and uses the values from whichever pixel is lightest.

The main difference between this and the Lighter mode is that the Lighter mode compares the individual colours in each pixel (not the total amount of light) and produces a colour that is different from either of the original two layers. You can see this most obviously in the purple tinges that were introduced at the edges of the grey areas in the Lighten example above).

Blending with black has no effect.

CONTRAST BLENDING MODES (50% grey neutral blend modes)

With this group of blending modes, 50% grey in the blendng layer has no effect on the underlying layer.

Any pixel lighter that 50% in the blending layer will lighten the underlying pixel.

Any pixel darker than 50% grey in the blending layer will darken the underlying pixel.

Because some areas of the image are being lightened and some are being darkened, the contrast will increase.

Blend mode: OVERLAY

This blend mode has an effect that is similar to Multiply in the dark areas of the original image (areas darker than 50% grey) and similar to Screen in the light areas of the original image (areas lighter than 50% grey). The effects are not quite so severe as using Multiply or Screen because the neutral colour is 50% grey rather than black or white.

The result is a saturated, high-contrast image with reasonable detail preserved in the shadows and highlights. However, it can produce colour shifts (as in the top right of the sample image).

Blend mode: SOFT LIGHT

This blend mode produces the same effect as Overlay, but it is much more subtle and is less likely to produce colour shifts.

When the blend layer pixel is white the underlying pixel wil be lightened but not made pure white. When the blend layer pixel is black the underlying pixel will be darkened but not made pure black.

The result is a more natural looking increase in saturation and contrast with well-preserved detail in shadows and highlights.

Note: This is a useful blend mode for subtle dodging and burning. Just add a 50% grey layer above the image and set the blend mode of this layer to Soft Light. Paint on this layer with a soft brush at low opacity. Painting in white will dodge, painting in black will burn.

Blend mode: HARD LIGHT

This mode is a direct combination of Multiply (for areas of the blend mode darker than 50% grey) and Screen (for areas of the blend layer lighter than 50% grey).

If the blend pixel is white the resulting pixel will be white. If the blend pixel is black the resulting pixel will be black.

It produces a harsher (more contrasty) result than Overlay.

Blend mode: VIVID LIGHT

This is a combination of Colour Dodge (when the blend pixel is lighter than 50% grey) and Colour Burn (when the blend pixel is darker than 50% grey).

Blend mode: LINEAR LIGHT

This is a combination of Linear Dodge (when the blend pixel is lighter than 50% grey) and Linear Burn (when the blend pixel is darker than 50% grey).

It is similar to Vivid Light except it changes the base layer brightness instead of the base layer contrast.

Blend mode: PIN LIGHT

This is a combination of Lighten (when the blend pixel is lighter than 50% grey) and Darken (when the blend pixel is darker than 50% grey).

It brightens the underlying image in the highlight areas of the blend layer, and darkens the underlying image in the shadow areas of the blend layer.

Blend mode: HARD MIX

This mode was new to Photoshop CS.

It produces a posterized effect (similar to Image>Adjustments>Posterize).

First it combines the pixels in the two layers using the Vivid Light mode, then it applies a "colour threshold" effect.

Pure black in the blend pixel produces a pure black result. Pure white in the blend pixel produces a pure white result. All other colours in the blend pixels produce pure colours in the result - red, green, blue, cyan, magenta or yellow.

COMPARISON BLEND MODES

These two blend modes compare the blending layer to the underlying layer, looking for identical pixels in each.

Blend mode: DIFFERENCE

This mode compares the pixels in the two images and gives black where the two pixels are identical. When the pixels are different the result is a colour that gets closer to white as the difference increases.

White on the active layer inverts the colours beneath it - You can see this in the bottom left and top right of the example image.

Black on the blend layer does not change the underlying image - you can see this in the top left and bottom right of the example image.

Mid-grey on the blend layer turns mid-grey on the underlying image to black - you can see this in areas of the sky around the middle of the example image.

Blend mode: EXCLUSION

This is similar to the Difference mode, except that mid-grey in the blend layer leaves mid-grey in the underlying layer at grey (rather than making it black).

In this example, as the blend layer makes a transition from black to white (on the left half of the image) the Exclusion mode causes the result to make a transition from normal to mid-grey and then to total inversion. With the Difference mode, this was a transition from normal to black to total inversion.

COLOUR BLEND MODES

These modes all substitute either the hue, saturation, colour or luminosity information from the blending layer for the corresponding information in the underlying layer.

In the examples used for the other blend modes (above) the blending layer contained no colour information (it was a pair of black-to-white gradients) so blending that with the underlying image simply produced a monochrome image. So that the effect of this blending mode (and the next three blending modes) could be demonstrated, the blending layer was changed to a blue-yellow gradient (left) and a red-green gradient (right).

Blend mode: HUE

This mode uses the hue values from the pixels in the active (blending layer) and combines that with the saturation and luminosity values of the underlying layer.

Blend mode: SATURATION

This mode uses the saturation values from the pixels in the blending layer and combines this with the hue and luminosity values from the underlying layer.

The colour (hue) of the blending layer makes no difference (the blue and red at the top of the example image produce the same result because they had very similar saturation values).

Note: Saturation determines how much colour shows in an image (how vivid it is). If there is no saturation then there is no colour - that's why "desaturation" produces a greyscale image. When a colour is completely saturated it is almost fluorescent.

Blend mode: COLOUR

This mode uses the Hue and Saturation values of the blending layer pixels and combines them with the brightness values of the underlying pixels.

The result is similar to using the Hue blending mode except the Colour mode can introduce colour into areas of the underlying image that did not contain colour.

Blend mode: LUMINOSITY

This mode uses the luminosity values of the blending layer pixels and combines them with the colour (hue and saturation) values of the underlying pixels.

This mode is very useful for preventing colour changes when you apply sharpening with Unsharp Mask - make the USM adjustments and then select Edit>Fade Unsharp Mask and set the blend mode to Luminosity. Do the same thing when you adjust brightness and contrast with Levels or Curves. (Better still, make those adjustments on an adjustment layer and then change the blend mode of the layer to Luminosity.)

LAYER SEQUENCE MATTERS

If you have two layers in an image file and you change the blending mode on one of them the result will sometimes depend on which layer is "on top" (i.e. which layer is the blending layer and which layer is the underlying image).

With the following blending modes the order of the layers makes no difference if the layers are different: Darken, Multiply, Linear Burn, Darker Colour, Lighten, Screen, Linear Dodge, Lighter Colour, Hard Mix, Difference and Exclusion

For other blending modes the sequence of layers does make a difference. For example, using Overlay and using Hard Light gives the same result if the order of the layers is reversed.

If the blend layer is a copy of the background layer, only certain blend modes will change the overall result: Multiply, Color Burn, Linear Burn, Screen, Color Dodge, Linear Dodge, Overlay, Soft Light, Hard Light, Vivid Light, Linear Light, Hard Mix, Difference and Exclusion.

THERE'S MORE!

All of the blending modes described above can be applied to LAYERS (as in the examples shown). They can also be applied to LAYER STYLES and to the PAINTING TOOLS. There are some other blending modes that can be used with the painting tools but which are not available as layer blending modes. These will be dealt with in another tutorial.

All images on this site and all documents and tutorials linked to this site are copyright.

This page last updated 25th August 2008 (RK)