If you found this article, you probably need to have a refresher on what image masking is and what it can be used for. Well, the first thing you should know about is layer masks in Photoshop. Unless you know how useful layer masks are, you can’t truly grasp the full potential of Photoshop. If you are not someone in the graphic design industry, you might not understand what a “mask” has to do with images. In the most basic of terms, when performing image masking, you would be applying something onto one single portion of a picture. In image masking, there are two main types of masks, layer masks and clipping masks. While these types have virtually the same core concept, the way they are applied is quite different.
When something is placed over another layer so the transparency of the first layer can be altered, that is a layer mask. It is most useful if you don’t want to change the entire layer opacity and just want to control one specific spot of the image. For example, if you wanted the entire layer to be at a different opacity, you could just change the rate. However, if you wanted only the upper half to be at a different opacity, you could use a mask to achieve the look you are going for. When you first apply a mask, you won’t be changing anything immediately; it will just be active for you to change. On this new layer mask, you’ll be able to draw in any variance of black and white (including grey). By painting over the first layer, you’ll be able to change the image underneath the mask. Painting in white will mean the image below will have 100% opacity and painting in black will give the image below 0% opacity.
As stated before, clipping masks do share some similarities to layer masks but clipping masks use a specific layer to change how transparent another is. When using a clipping mask, you would put a layer on top of another and use the bottom layer to change how transparent the top layer is. You also will not use the black and white paint like in layer masks. Instead, a clipping mask will use the different transparencies of the layers that make up the entire image, with the bottom layer having the most effect. So, if you use a bottom layer with varying area of opacity, this will show in the top layer.