A Look at GIMP Layer Blending Modes

In my last post I talked about GIMP Layers. You can do a lot with layers just playing with the Opacity Slider using the default “Normal” blend mode. But don’t stop there! There’s a whole lot of fun to be had using the other Blend Modes!

The Blend Modes control how the layers blend, or combine, with each other. When you set the Blend Mode for a layer, you are controlling how that layer combines with the layer directly below it. Most of the Blend Modes (other than Normal and Dissolve) mathematically combine the two layers which is why they can create such neat affects like in my photo of Pluots.

There are 21 Layer Blend Modes available in GIMP. I know that’s a lot but don’t freak out. Any tutorial that requires a Blend Mode other than Normal will tell you which one to use and when. If you just want to try them out on your pictures, clicking through all of them to see what you get is pretty fast and super easy. This stuff doesn’t have to be memorized to be useful. Remembering that these options are there is the important part even if you don’t remember exactly what they do. On that note here’s exactly what 15 of them do.  My interpretation without all the equations is after the jump.

Normal

This is the default Blend Mode. It causes the selected layer to sit on top of the one below it. No math and no funny stuff. If you make the selected layer transparent with the Opacity Slider it will look like it blends with the layer below it but it doesn’t really. You can get a lot done with just Normal Mode and playing with the Opacity Slider.

Dissolve

This one makes random pixels in the selected layer transparent so you can see the layer below through those pixles. It only works if there is an alpha channel (which lets you use transparency) in that layer. You can add an alpha channel to the layer by right clicking the layer icon (two-finger tap on a Mac) and selecting Add Alpha Channel. To be honest, on it’s own this Mode looks a little like a cheesy Star Trek effect.  Now that I’ve admitted that, I’ll be on the hunt for a use of this Mode that makes me feel differently. I’ll let you know when I find one.

Multiply

Just like it sounds this Mode multiplies the colors in the selected layer with colors in the layer below it. The result will be darker than either the selected layer or the layer below.

Divide

This Mode basically divides the colors of the lower layer by the colors of the selected layer. There is some more math thrown in to make sure the Divide Mode actually works consistently. The result will always be lighter and can even be “blown out” or completely white.

Screen

Like Divide, Screen lightens an image. Unlike Divide, Screen won’t have parts that “blow out” or turn completely white.

Overlay

This combines the affects of Multiply and Screen. If the image is  dark it will tend to get darker, and if it’s light it will tend to get lighter.

Dodge

Overall brightening.

Burn

Overall Darkening.

Hard Light

Screens or Multiplies depending on the color of the bottom layer. Parts of the bottom layer that are light will be Screened, parts that are dark will be Multiplied. This mode can make things look pretty vivid. (My interpretation of emptyeasel.com)

Soft Light

According to what I’ve read, this mode darkens or lightens depending on the bottom layer. So it’s similar to the Hard Light Mode. But it just darkens or lightens, rather than Screening or Multiplying so the affect is different. (Interpretation of emptyeasel.com)

Grain Extract

I can’t figure out what this does exactly but if you’ve got GIMP you’re in luck b/c Photoshop doesn’t have this one.

Grain Merge

This looks like the opposite of Grain Extract. But like Grain Extract, I can’t figure out exactly what it does, and it’s unique to GIMP.

Difference

Makes images darker without clipping to black. Clipping means the color has gone outside a usable range so the closest color within that range is used instead. In this case no colors have gotten so dark that they just show black.

Addition

This Mode is always as light or lighter than the selected layer or the layer below it and can even become white.

Subtraction

Like Difference, Subtraction makes images darker. Unlike Difference the result can clip to black.

Darken Only

Only the darker color of the two layers (the selected layer and the layer below it) will show.

Lighten Only

Only the lighter color of the two layers (the selected layer and the layer below it) will show. This one is really useful to use when retouching portraits.  Think under eye circles and blemishes.

Hue

The color, or hue, of the top layer remains the same. The saturation (intensity) and value (lightness or darkness) of those colors are determined by the layer below. In this case, since the gray layer has no saturation, the top layer becomes completely desaturated. The gray layer also has uniform value, or lightness, so all of the detail is lost and we just see plain gray.

Saturation

The saturation of the selected layer remains the same. The colors (hue) and value (lightness or darkness) are taken from the layer below.

Color

The color and saturation of the selected layer remain. Those colors take on the lightness or darkness of the layer below. Notice the shadow areas around the fruit. They are more saturated but not any darker than the highlight areas. That’s because the gray layer doesn’t have any highlights or shadow (areas of lightness or darkness) to give the top layer.

Value

The color and saturation of the layer below are kept. The colors take on the lightness or darkness of the selected layer. Here we just see the highlights and shadows of the top layer.

You Made it! And So did I!! Remember it’s really easy to flick through all of these options when you want to try something new. Trying these out is ‘non destructive’ meaning it won’t permanently change your pixels. You can always go back to Normal. Have you noticed yet that you have Modes on your Tool Options? They work the same as the above but the effects are localized to whatever you’re brushing. Remember how I mentioned that the Lighten Only Mode is good for skin retouching? Try it with the clone tool over blemishes. It really helps those clone stamps look natural.

Next up I’ll talk a bit about Layer Masks. They’re like a spa treatment for your photos.