I had a request for an explanation of exactly how masks work, and some useful techniques that come in handy a lot. I wrote before of some easy ways to mask solid color backgrounds, but I wanted to add some simple, but highly effective techniques too.

The basic premise of a mask is to eliminate portions of an image from view, without actually affecting the image itself. A mask can be applied to a single layer or a group. Masks operate with simple rules: dark masks, and light reveals, with the shades of gray masking relative to their darkness.

For absolutely no reason at all, I’m going to demo masking by replacing a man’s head with a giraffe’s.

The two photos I used to create this came from my favorite stock photo site, sxc.hu.

• Man in costume with tie 5
• Giraffe Close-up (props to Johnathan By)

There are multiple ways to apply layer masks, but I’ve found only one to be really practical. Since I always have my Layers palette open, I use the button at the bottom specifically for this.

If you have a selection active, and then click this button, it will mask everything outside of what you have selected–a quick way to do masks too. Oftentimes, I will apply the mask, and then proceed to begin masking using the Brush tool, selections, or gradients.

The mask used here was applied to the picture of the giraffe’s head, to eliminate the background in the image, and also to mask around the collar of the man’s shirt. Essentially, what’s happening is something like this:

The result is not exactly satisfactory, though.

I’ve got some of the man’s head still peeking out, so in order to correct that, I’m going to use the Clone tool with a large-sized Soft Mechanical brush from the Basic Brushes set to wipe his face out. This is where carefully selecting a good picture comes in handy–a more complex background would require a lot more effort to eliminate his face.

The final touch is to use the Burn tool around the bottom of the giraffe’s neck near the collar to add some shadowing for a more-convincing merging between the giraffe and the man’s clothes.

The final result, again:

Some general tips when doing this sort of work:

• Keep proportions in mind and do your best to get everything sized properly before beginning to mask.
• When hunting for pictures for this type of composition, I find it’s best to use tabbed browsing to quickly flip back and forth to size up whether the angles, lighting, and various other factors will be workable. Pick a primary image, from which the suitability of other pictures will be judged against. The suit was the primary picture in this case, and I searched for giraffes that were looking in a realistic direction similar to the man’s.
• When masking, the keyboard shortcut for switching from foreground to background colors is typing “x”–this lets you quickly mask and unmask portions, giving you lots more flexibility while using the brush tool.

I’ll continue to discuss the myriad uses of masks in another tutorial, focusing on the ways textured brushes and gradients can create some really stunning compositions.