Blend layers

- [Instructor] Previously we looked at how to control the opacity of content in layers. Now it's time to take it a step further and see how to use layer modes, also called blending modes, for mixing layers. Some of these modes are very useful and important to understand, others you probably won't use very often, if ever. So I won't get into the details of every single mode, but I will explain the types of layer modes and highlight some of the most useful ones, and in the exercise file I've put a layer with five bands going from black on the left, to middle gray, to white on the right, and I'll apply several layer modes to this layer to illustrate them, and the first thing to understand about using layer modes to blend layers is that you need at least two layers for there to be any effect, and you apply the layer mode to the higher layer in the layer stack to create the effect.

So I'll select the gray band's layer, make sure it's visible, and start exploring the mode menu. Notice on the far right there's a choice here between the default layer modes and legacy. We're just going to look at the legacy modes. The default modes add a few new choices and can produce different results, and you can experiment with them on your own once you have a basic understanding of what layer modes do. Right below normal and dissolve we have five groups of layer modes, and they're grouped according to the kind of effect that they have.

The first group lightens colors. Of these, screen and dodge might be the most useful. Screen lightens the image when you apply it to any color other than black. Black is transparent when you apply screen to it, and white completely replaces the image. Dodge is like screen but it adds more contrast and saturation, and this is a pretty extreme effect, but remember, you can always lower the opacity of a layer at the same time you apply a layer mode to lessen the effect.

So I could take this down to something like 50%. I'll set it back to 100, and then we have layer modes for darkening. Multiply is the opposite of screen. It darkens the image when you apply it to any color other than white, so white becomes transparent when you apply multiply to it, and black completely replaces the image. Burn gives you a more saturated, high contrast look because it leaves some of the light colors still visible as it darkens most of the image.

Next, we have three modes that emphasize contrast by making dark colors darker and light colors lighter, but they don't affect saturation, and the first is overlay. Notice that on the left side of the image with the black band, things get darker when I apply overlay, and on the right side with the white band, the underlying image got lighter. Soft light is similar to overlay, and hard light is like a combination of multiply and screen. Middle gray becomes transparent, white makes everything white, and black makes everything black.

The next group of layer modes you might not have much use for, but I'll just mention that difference creates some extreme special effects, as lighter colors invert the image while darker colors have no effect. Subtract is like the inverse of multiply. With subtract, lighter colors darken the underlying content, and dark colors have no effect. And finally, to show the last four modes, I'll turn off the gray band's layer and turn on and target the purple layer.

HSV hue takes just the hue value of the blend color and blends it with the saturation and value, or luminosity, of the content beneath it. So when I apply the hue mode to this layer, I can see that de-saturated areas like the shirt and the surfboard stay de-saturated, and the lights and darks are unaffected, but the purple hue is applied to everything. HSV saturation takes just the saturation of the purple color here, which is fairly low, about 25%, and blends it with the hues and luminosity values of the underlying layer.

So now all the colors have a uniform 25% saturation, or if I apply this mode to a layer with no saturation, like black, white, or pure gray, it de-saturates the content underneath it. I'll turn off the purple layer, and turn on the white layer, and set it to saturation, and it de-saturates the content below it. I'll switch back to my purple layer and set it to HSL color.

This one takes both the hue and saturation values of the blend color and mixes them with the luminosity of what's beneath. So, in this case, nearly everything gets colored purple. I'll turn off the purple layer, turn on the aqua layer, and target the surfer layer, and the last mode, HSV value, does the opposite of color. It retains just the luminosity, or value of the blend layer, and mixes it with the colors underneath.

So I can use it to completely replace the color of the surfer layer with that of the underlying aqua layer and create a duo tone effect, and finally, I just want to point out a little shortcut for quickly going through the different layer modes when you're experimenting to create an effect or when you just don't remember which mode does what. When you choose a layer mode, like say darken only for our surfer, at this point, the layer mode has focus, and you can tell that by this little dotted line around it. So you can use the up and down arrow keys on your keyboard to cycle through layer modes, and I'll press my down arrow key to compare the effect of some different layer modes.

Blending layers is a totally nondestructive way of manipulating content so you can always tweak things and go back to your original image if you want to with no risk. So go ahead and have fun and explore what you can do by blending layers in GIMP.