Aperture and Depth of Field Lesson

Aperture and Depth of Field 

Now that you understand that aperture, shutter speed, and ISO can control your exposure, it's time to take a deeper look at each of these settings.

Remember that aperture is the size of the opening in the lens when a photo is taken. The opening controls how much light can enter your camera when the shutter is open. The aperture settings are called f-stops and are represented by numbers (i.e. f/1.8, f/2, f/8, etc). The bigger the number, the smaller the lens opening. 

The other primary function of aperture is controlling the depth of field of your image. This is why aperture can be important to the artistic aspects of your compositions. 

Depth of field is a measure of how far the field of focus is in a photograph. It is the amount of distance between the nearest and farthest objects that appear in sharp focus in a photo. 

The size of the aperture opening determines the depth of field, or how much of your scene is in focus. Lower (smaller) f-stop number means less depth of field or "shallow" depth of field. When your aperture is wide open (smallest f-stop number), your focus will be much shallower and there will be fewer things in your photo that will be in focus. Moving on from one f-stop to the next doubles or halves the size of the amount in your opening lens (and the amount of light getting through). 

Note: a smaller f number means a bigger aperture. For example, a f/2.8 will be bigger than a f/22.

On the opposite end, higher f-stop number, which means smaller lens opening, will allow for a deeper focus which means that more things in your photo to be in focus.