Layer masks allow you to control what parts of a layer you want to hide or show. The layer mask is a greyscale bitmap image, that uses white to reveal parts of an image or black to hide parts of an image. Greyscale values can also be used to create a transparent effect which is very useful when blending between images. An easy way to remember what white and black do is to remember this saying:
White reveals and black conceals
The important thing about layer masks is to remember they are just images. Which means you can edit and modify them just like any other image – just remember they are greyscale images. Also layer masks are non-destructive, so you will never damage the original image.
Next we will look at hiding the rather boring sky in the Lodge layer and show the more interesting sky on the sky layer below.
Creating a layer mask with a selection
A simple rule to remember when creating a selection to make a layer mask is to: select to show. This means that anything you select will remain showing and anything that is unselected will be hidden when the layer mask is created. Lets see this in action.
To select the hunting lodge and the grass in the foreground I used mainly the Quick Selection tool. You will need to spend some time making the selection as best as possible as the selection will affect the quality of the layer mask. Keep a look out for future blog posts about selections.
With the lodge selected it is time to create a layer mask.
To create a layer mask we can click on the Add a mask button at the bottom of the Layers panel, which looks like this: .
The area of the image that was selected is represented as white in the layer mask so showing that part of the image. The area that was unselected is represented as black, so hiding those parts of the image.
Here is the image composition now, with the original sky hidden and the Sky layer showing through.
There is still work to be done with this image, such as a better colour match between the sky and the lodge. I hope you will use the principles of using selections to create layer mask to make your photoshop work better and more interesting.