One of the easiest ways to restrict the way that an adjustment layer blends with the layers below is by using blend modes. Typically Photoshop’s fill and adjustment layers affect both the colors and the luminosity values in an image. However, there are times when we want to isolate the effects of the adjustment to just a single component, like hue, saturation, or luminosity or color. So in this first example it’s probably the most obvious. I want to add a color wash over the image.
Use this image
From the bottom of the layers panel I’ll choose gradient. And I’ll select a gradient from the presets here. This is a gradient that I previously created. And then click OK in order to apply it. However, we can’t see the luminosity values of the layer underneath. So from the layers panel I’ll change the blend mode to color. Now I actually want to reverse that gradient so I can double-click on it, and then just choose reverse. I could also lower the opacity if I thought it was too strong. All right, let’s toggle off the visibility of that layer. In the next example I’m going to add a curves adjustment layer. We can see from the histogram that this image is quite flat. It doesn’t have any dark values or very light values. So I’ll move the black point slider over to the right, and the white point slider over to the left. But by making such a dramatic change, I’ve also added a lot of saturation to the image. In order to remove the saturation so that Photoshop is only adjusting the luminosity values, on the layers panel from the blend modes drop down menu, I’ll choose luminosity. We can see if I undo this using Ctrl + Z. That’s with the saturation in normal mode. And if I use Ctrl + Alt + Z to move forward, there it is, set to luminosity.
In this third example I want to lighten and darken the luminosity values, but only of specific color ranges in the image. And I want to keep the image in color. If I add a black and white adjustment layer, that’s going to take the image to black and white. But if I change the blend mode to luminosity, then it’s going to leave it in color, but I still have access to all of the different color ranges. So I can select my on targeted adjustment tool, and then click for example, in the blues, and drag to the left in order to decrease the luminosity values, darkening them. Or I could click in the grasslands in the foreground and drag to the right in order to lighten the luminosity of the yellows. Finally, in the last example I want to change the hue, so I’ll add a hue and saturation adjustment layer. Even though I’m not going to touch the saturation slider, when I move the hue slider around, it is actually changing the saturation. So in order to isolate it to only change the hue, I will select that, preventing the other components in the image from being affected. Of course, you can use a combination of all of these. So in this case, because the image was so flat, I might want to also view the curves adjustment layer.
So the next time you want to isolate the effects of an adjustment layer, try using the individual component, such as hue, color or luminosity blend modes.