Have you ever wondered how to use an image as a mask in Photoshop but just couldn’t figure out how to do it? The solution is actually fairly simple, but Adobe hasn’t done you any favors with how unintuitive it is. With just a few easy steps, you can use any picture or graphic to mask specific parts of a layer.
The first thing to consider is the fact that low-contrast images are not going to work well as masks, since they are going to be converted to grayscale when placed on the layer mask. Make sure the blacks in your image are completely black, and the whites are completely white. I like to mess around with this a bit by selecting the layer I want to use AS the mask, clicking “Image” at the top, then mousing over “Adjustments” and then selecting “Levels.” Ctrl/Cmd + L works as well. I like to drag the whites down quite a bit and the black up quite a bit, depending on the image, until a good chunk of the image is solid black and white. This allows for better masking.
Now for the actual masking. Follow these steps to place the photo or image as the layer mask on another layer.
Note: I am using Photoshop CS5
1. Select the layer you wish to turn into the mask.
2. Press Ctrl+a (Mac: Cmd+a) to select the contents of the photo in their entirety.
3. Pres Ctrl/Cmd + c to copy those contents.
4. Create a layer mask on the layer to be masked by selecting the layer, and then pressing the “Add Layer Mask” Button at the bottom of the layers palette.
5. Here is the magic part. This is a little trick they won’t teach you in design school. (Disclaimer: I have no idea what they teach you at design school, I’ve never been). To treat a mask almost as it’s own, normal layer, you just hold down Alt (Option) and click on the layer mask thumbnail. This let’s you view the mask by itself, and also make changes to it. For some reason it seems like the good folks at Adobe don’t want you using this feature, I’m not quite sure why.
6. Press Ctrl/Cmd + v to copy the image into the mask. Alternatively, you can press Ctrl/Cmd+Shift+v to copy the image in place, preserving it’s original location in the document.
7. Hide the layer with the original image.
That’s it! Click another layer or elsewhere to see how the mask looks. There are a lot of possibilities with this method, use your imagination!
I also have a separate tutorial showing you how to use a shape as a layer mask.