The opacity or transparency of a layer is usually seen as a kind of gradient—the layer can be fully opaque, fully transparent, or somewhere in between. But did you know that you can control the opacity of particular parts of a layer without selecting them manually? It may not sound very useful at first, but just think about blending photo textures! Interested?
What is Blend If Blending?
To present blending we need two elements: an upper layer and lower layer(s). Let's say we have this purple sphere (lower layer):
And we want to blend it with this gradient (upper layer):
If we double-click the upper layer we get a window with a variety of options.
It's commonly used to set Styles for the layer, and the Blending Options, the default view, is usually ignored. But if you look down at the Blend If section, you'll see two black and white sliders. Once you get to know them, they'll do magic for you!
Download the attachment to follow my actions. This way you'll remember it better!
Each of the sliders has two markers: black (left) and white (right). Everything on the left of the black marker is transparent; so is everything on the right of white marker.
- The shades in this section are transparent, because they're on the left of the black marker.
- The shades in this section are opaque, because they're neither on the left of black marker, nor on the right of white marker.
- The shades in this section are transparent, because they're on the right of white marker.
As long as the markers stay on their ends of the slider, they have no
effect. You need to move them to make them work. Let's see what they're
The This Layer Slider
The first slider is labeled "This Layer". Grab the black marker, drag it to the right, and see what happens to the shades shown on the left.
Just as we've described, when you expand the area on the left of the black marker, the shades the area contains become transparent in the layer. The same happens when you drag the white marker.
Because you can move both markers individually, a confusing situation may occur:
- White marker says this area is opaque.
- White marker says this area is transparent.
- Black marker says this area is transparent.
- Black marker says this area is opaque.
As a result, the white marker trespassing the transparent area of the black marker brings its "opaque left, transparent right" with it. It may seem complicated at first, but you need to remember just one rule: when the markers switch places, they work just the other way around.
Split the Marker
I've told you that each slider has two markers, but it's not completely true. Each of the markers can be split in two. Just drag the marker when holding Alt. This way you can make the change of opacity more gradual and not so apparent.
The Underlying Layer Slider
The other slider works in an even cooler way. The shades on it have nothing to do with the layer we're working on—it's about the shades of the lower layer(s).
The general rule doesn't change at all, but this time it's better to word it like this:
- The area of the layer lying over the shades of the left side of the black marker is transparent.
- The area of the layer lying over the shades of the right side of the white marker is transparent.
You can also split any marker to make the change gradual.
Change the Opacity of a Texture
I've presented this mechanism on a grayscale gradient, but it's not required. Blend If sliders are great if you want to adjust a texture to the object. Just look:
You can also still use Blend Modes safely—they treat that "new opacity" as something normal!
Blend If in Practice
But what can we do with it? A lot of cool stuff! Let's say we want to finish this dragon foot. It's almost done, it's colored and shaded, but it's a bit boring. What can we do to make it look better without destroying what we have achieved so far?
If we want to give all the shadows a trendy bluish tint, we can create a New Layer, clip it (Control-Alt-G) to the base, and fill it with blue.
If you change the Blend Mode to Color, it will colorize the base. But we want to colorize the dark parts only!
Let's go to Blending Options and drag the white marker to the left. Those parts of the blue layer that are over light areas will become transparent.
Let's split the marker by holding Alt to make the border less apparent.
We can do the same with light! Create another layer and fill it with the color of the main light source.
Change the Blend Mode to Soft Light and lower the Opacity.
This time drag the black marker to the right.
And soften the effect:
Let's check another cool trick. If we want to make the scales shiny, we can add a spot of highlight to every single scale. But there's an easier way. Create a New Layer and paint bright bluish strokes just where the strongest light should hit.
Now make the parts over crevices transparent.
One more trick. I've added a texture to the foot and set the Blend Mode to Overlay. Unfortunately, this mode makes the foot much brighter under the bright parts of the texture, and darker on the dark side.
We can remove the white parts to get rid of this effect.
We can also leave the texture visible only in the light (the texture was adding more darkness to our shadow, and that wasn't our intention).
Compare these two. That final rendering we have just made took no more than five minutes, but it certainly doesn't look like it! Just keep in mind that for this to work you need to have the lighting well defined first. You can't expect Photoshop to do everything for you!
That little trick you have just learned will help you in many applications. I've also used it extensively in my Harness the Elements series, so it may be easier for you now! It's more of a tool than a trick, and I'm sure you'll find a lot of ways to make your artworks look better rendered in less time thanks to it.