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Layer Masks are used to:
- Erase areas of a photo.
- Select an area of a photo to apply an effect.
- Apply Adjustment Layers selectively.
- Combine photos in one canvas.
- …and much, much more.
Whenever you have an icon in the second column in your layers panel, that’s a mask.
Raster Layer Masks
A raster layer mask is a greyscale image, where darker pixels hide the underlying photo to increasing degrees. It works a bit like a dimmer on a light switch. The darker the pixels are on the mask, the less you can see the photo on that layer.
The difference is that you can paint a gradient on a mask. The darker the gradient gets, the more the photo will get hidden.
You can mask content by:
- creating a mask, then painting with black, white or grey.
- creating a selection, then creating a mask.
There are more techniques for creating masks, but these two will get you started.
Vector Layer Masks
A vector layer mask hides all content on that layer outside of its vector shape(s). You can draw the vector shapes right on the mask, or you can copy/paste them from anywhere. The two major benefits of vector masks compared to raster masks is that vector masks are sharp-edged and they’re scalable.
If you want to mask something with the absolute sharpest edge possible, use a vector mask.
Lets start with replacing the background on a photo by hiding the original one to reveal the one on the layer below. In this case, we’ll change the background to a beach scene.
Masking to Blend Photos
We can also use masks to blend photos. We’ll use the Gradient Tool on the mask. Since black hides and white reveals, this will make the photo on the top layer gradually become transparent to partially reveal the photo below.
Masking with a Photo
A Layer Mask is a greyscale image. Where the pixels are dark on the mask, they’re hiding whatever’s on the layer below. Where they’re light, they reveal what’s on the layers below. It stands to reason that if we paste a photo onto a mask, it will do the same, hopefully giving us interesting results.
We’ll use content from two stacked layers to take the best elements from each photo. In the end, everyone will have a smile on their faces. We’ll use Auto-Align Layers and Layer Masks to accomplish this. You’ll see; it’s pretty cool.