Let’s say I have a picture of a dog like this:
And I would like to change the background that he’s in. For example, let’s say I want to put him in a setting like this:
First, I would have each image on a separate layer with the picture of the dog on top like so:
Now I am going to click on the “Add Layer Mask” button at the bottom of the layers window:
After I select “Add Layer Mask”, I will select the paintbrush tool and paint over the current background of the dog picture. I must make sure that black is selected as my color to remove the background. If I make a mistake and want a portion that I have erased back, I can just switch to white and paint over said portion again.
This is why I am using the Quick Mask method instead of just erasing the background.
Mission accomplished. Yes, the dog is a little large for this particular background, but that wasn’t really the point of this little tutorial, so let’s just overlook that. If we wanted the dog smaller we could have just resized the layer with a simple Free Transform to begin with.