The term depth of field describes how much of your photo will be in focus. The camera tool now allows you to control how much is in focus using Depth of Field. But the way that controls how much is in focus is to do with the aperture of your camera. If you're an old school photographer you'll understand how aperture relates to depth of field, but if you're a modern digital camera photographer you may not understand this. In simple terms the larger the number for the aperture (f-22) the more will be in focus, the smaller the number for the aperture (f-2.8) the less will be in focus.