What is a layer mask in Photoshop? And why are they so important?

Question

You "paint" on Layer Masks in Photoshop to erase or reveal objects in your composition. The Photoshop "Eraser Tool" should not be used—Layer Masks allow you constant access to edit your Layers if and when you need to go back and touch up. When you're on a Layer Mask you "paint" with black to erase and "paint" with white to reveal. A handy tip is to press the "x" key to switch back and forth between black and white. Also take note of your brush "hardness" and "softness"—hard brush for straight edges, softer brush for a softer edge.

Answer 1

Layer masks are super important because they are nondestructive to our working process!

A hypothetical: a photo is on a rasterized layer (it isn't a smart object, so you can erase or edit it). You want to take out a bit from the edge, so you erase it with your eraser tool. This practice was destructive. If you end up erasing too much, all you can do is undo, and after a certain number of actions, it is totally irreversible.

However, layer masks only affect the transparency settings of pixels in a layer. For instance, if you make a mask on top of that layer, you can make pixels disappear by painting in black with your brush tool. Black=0% opacity. But then, if you paint back over with white, it will be visible again! White=100% opacity. You can even set different greys, and they will show different degrees of opacity accordingly! To make this process super convenient, switch back and forth between black and white with your X hotkey, and you can erase and add back as needed!

Hope this helps! :)

Answer 2

A layer mask in Photoshop is a layer modifier that allows you to hide parts of a layer. This is important because it protects the original layer from damage. The eraser tool gets rid of information stored on a layer, and is very hard to fix once you have done it. Using a layer mask can save your original work, in case you make a mistake or change your mind. There are a lot of interesting tricks with layer masks that can help you create original looks. In general you will apply a layer mask to the layer, click on it. Then you will paint in the workspace with black or white to affect what is visible.