Aperture is a hole in your lens made up of little metal plates that work together to open and closed it controls your depth of field. Large Aperture means a large hole and Small Aperture means a small hole. However, don’t get confused with the f Stop number that goes with it. A large aperture (large hole) has a small number (i.e f2.8) and a small aperture (small hole) has a large number (i.e f22).
APERTURE CONTROLS DEPTH OF FIELD
Depth of field is the amount of your photo that you have in focus. You control this by changing your aperture. A small aperture (large number f22) will give you greater depth of field. This means that most of your photo will be in focus. A larger aperture (small number f2.8) will give you shallow depth of field. This means that only a very small portion of your photo will be in focus.
FOCAL PLANE AND FOCAL POINT
Think of Depth of Field as a three-dimensional effect, with an X, Y and Z axis. The focal point is the point that you are focused on. Aperture controls the depth of field (Z) beyond and before that point. This is the Z axis. The focal plane (X and Y axis), is the plane of focus. Anything in line with that plane either side to side or up and down will be in focus.