Talk to anyone who uses Photoshop a lot and they seem to fall into two groups: those who love layer masking and use it every day - and those who don't even know how to get started with it. The truth is that layer masking is one of the most powerful parts of Photoshop and its only limit is your imagination - but it's also dead easy. The underlying principle is so simple that you can learn it in two minutes and once you grasp it there will be no stopping you.
In a series of tutorials, we'll be looking at layer masking from the basics right up to the incredibly powerful things you can do with it. This is the first part so we're going to take it easy. First off - what is layer masking?
A layer mask allows you to show or hide parts of a layer by painting white or black on it. It's as simple as that. Let's look at an example.
Open a picture in Photoshop - for this tutorial it helps if it is a nice colourful image so I used a red tulip.
For a layer mask to work you need some layers so from the Layer menu, select new layer via copy. Your main image will not change but if you look in your layer palette you will see that Photoshop has duplicated your image into a new layer.
So that we can see what the layer mask does we need to make the two copies different - otherwise we can't tell what is going on. We could do anything to one copy but we'll keep it simple and obvious. Making sure you are on the new layer (just click it in the layers palette) go into the Image menu and choose adjustments and then desaturate. This isn't a very good way of making a black and white image but it is an easy way of getting a big difference between the two layers.
Here's how my image looks now. If we look in the layers palette we can see exactly what has happened. There are two layers. The top one is black and white and the one below it is in colour. Since they are both fully visible we just see the black and white one since it's at the top. If this is new to you then click the little eye next to the black and white layer to turn it on and off. See how the picture changes from black and white to colour as you show and hide the black and white layer.
Now make sure both layers are visible and that you are working on the black and white layer (click on it in the palette). From the Layer menu select Layer Mask and then Reveal All from the flyout. Your picture won't change at all but there's an important change in the layers palette. Photoshop has added a white layer mask to the top layer (this screenshot is from Photoshop CS2 - earlier versions look a little different from this but contain the same information).
White in a layer mask says “show this layer”. Black in a layer mask says “show the layer below”. To test this, make sure you are on the layer mask (not the layer), set your foreground colour to black and select the brush tool. Click with the mouse and drag your brush right across the middle of the picture. Everywhere you draw with black, Photoshop hides the top layer and shows you the layer below. That's it, that's a layer mask!
The first question most people ask is “couldn't I just use the eraser?”. We'll see in later tutorials how layer masking is much more powerful than the eraser but here's just one way it's better. Here I have drawn a big black square on the mask and it has shown an area of the coloured layer through it. That's just like erasing part of the top layer - except that I can paint with white on the layer mask like this. I can undo some of the erasing. If I save the file in Photoshop's PSD format then the layer masks are saved with it. I could open the file a month later and still undo some of the things I'd erased.
In the next tutorial, we'll look at some of the more advanced features of layer masks but before then, you might like to practise on some of your own pictures. Remember always to work on a copy so your original isn't affected and remember that it isn't just limited to black and white conversions - you can use any two layers and mask one onto the other.
Here are some examples that I have done using just two layers and the black and white paintbrush on a layer mask.
Now that you know the basics - why not experiment with layer masking? We'd love to see your masterpieces in the gallery.
Layer masking in Photoshop Elements
Layer masking isn't supported in Photoshop Elements but here's a great technique to mimic the effect.
Add a solid colour adjustment layer between the top layer and the background. It doesn't matter what colour you use. Click on the top layer in your layer palette and press Control-G (Apple-G on a Mac) to group the layers together. Your layer palette should look something like this. Now you can use the layer mask of the adjustment layer just as you would a mask in Photoshop - without paying the extra £500!
Layer masking in Paint Shop Pro - Courtesy of Andrea Lane
Duplicate your layer, Ctrl + C.
Paste it as a new layer, Ctrl + L.
Desaturate it, -> Adjust Hue/Saturation/Lightness Shift + H.
Click on colorize box, hue, saturation and lightness = 0.
Layers | New Mask Layer | Show All.
Paint with Black and White as for Photoshop to create the layer mask.
