It wasn't until recently that I discovered the awesome power of layer masks. Now I can't imagine how I worked without them! I use layer masks with every image I work on.
Layer masks are useful when you want to make "selective" changes to an image.
Many times, people make the mistake of applying a filter to the entire image, when only a portion of the image needs adjusting. And often, the effect is too strong. Layer masks will allow you to apply filters/adjusments to just the areas that need it, and give you the ability to control how subtle or strong that adjustment is applied to your image. Bonus: You don't have to make selections (but you can).
It's So Easy!
Instead of reading a lot of text about why and how this works, let's just jump right into it. Practice the following steps a few times, and before you know it, you'll be saying to yourself, "It's so easy"!
This image doesn't have a lot of damage, just a few spots on the face that I'd like to clean up. You could use the clone tool of course, but imagine that a large portion of the image was spotted, would you really want to "click and clone" the whole thing? For this tutorial, we're going to clean it up using a layer mask. Keep in mind that this is not a tutorial for cleaning images, it's about the layer mask.
Here's the "Before & After".
Duplicate your "Background" layer. You should now have two layers in your layer palette.
On the topmost layer ("Background copy"), apply the Dust & Scratches filter.
We got rid of those marks on his face, but we really messed up the details didn't we? Here's where the Layer Mask comes in.
- Hold down the Alt key while pressing the layer mask button on the bottom of the Layers palette.
This will add a black layer mask along side the image. A black mask will hide the image it's connected to - in this case, it should be hiding the top layer where we applied the Dust & Scratches filter.
Now your Layers palette should look like this:
Let's take a minute to look at what we have. We have our damaged layer on the bottom (Background), a top layer with a filter applied (Background copy) , and a layer mask that is hiding that filtered layer.
Now we are going to paint on the layer mask.
Set White as your foreground paint color.
Select a Brush from your brush palette (a small brush with a minimum feathered edge should do)
Click once on the Mask, to be sure that we are painting on the mask and not our image.
Start painting over the little black marks on the face that you want to eliminate.
You should see the marks disappear.
What we are doing is revealing parts of the topmost layer that has been hidden.
Take a look at the image below. You will see the areas where I've painted.
TIP: If you make a mistake, select Black as your foreground paint color, and paint back over the white areas. This will reapply the mask.
Once you've cleaned up your image, you can tweak it further by adjusting the Layer Opacity. Very often I will try lowering the opacity so that the flaws are hidden, but the effects of the filter are lessened.
At this point you can flatten the layers and you're done!
Practice this technique using other filters and adjustments. For example, instead of applying the Dust & Scratches filter, you could apply a light Gaussian Blur to soften the skin. Then, after applying the layer maks, use a brush with a low opacity setting to paint over the rough areas (avoiding the eyes and other important features, of course).
Here's a brief summary of the steps:
- Duplicate the Background layer.
- Apply a filter or adjustment to the Background copy.
- Add a layer mask to the Background copy (Alt+Add layer button).
- Select white paint, click once on layer mask, begin painting.
- Check opacity and flatten image.
Tip to remember for Layer Masks: Black hides the image it's connected to, White reveals the image.