The APERTURE is the opening created by a set of overlapping metal blades, known as the diaphragm, inside a photographic lens. This opening controls the amount of light coming through the lens. The wider the aperture, the less depth of field you capture. The smaller the aperture, the deeper the depth of field.

The FOCAL LENGTH of the lens determines the image magnification. The wider the lens, the shorter the focal length. This allows you to capture a deeper depth of field. The longer or more zoomed in the camera lens, the shallower the depth of field.

Interesting Characteristics of DOF

You will notice that as the depth of field increases, it does not do so equilaterally from the focal point. Meaning if you were to focus 10 feet away, and your total depth of field was 2ft at a given aperture, it is not true that the focus range is exactly 9 – 11ft away.

The majority of your total depth of field exists beyond the focal point. This is because the increase in DOF is an exponential growth with larger apertures and further focusing distances. As you increase the viewable range of an exponential pattern from a given point, you will have much larger integers towards the positive end of the scale. This is why more is in focus beyond your focal point than in front of it.

DISTANCE to subject refers to the length between the camera and the focus of the image. The closer the camera is to the subject it is focusing on, the narrower the depth of field will be. Inversely, the farther away the subject is from the camera, the wider the depth of field will be.