The 3 Factors...

There are three factors that affect Depth of Field...

1.    Focus Distance

This affects depth of field because the closer the subject of the photograph is, the shallower the depth of field tends to be whereas the depth of field tends to be deeper when taking photographs of landscapes for example. So the depth of field will differ when taking a photo of an object 1m away as opposed to 10m away.

2.    Aperture

When the aperture is larger e.g. f/1.2, the depth of focus is narrower therefore more of the picture appears unfocused (shallow depth of field). However, when the aperture is smaller e.g. f/22, it creates a sharper picture in terms of depth of focus (maximum depth of field).

Shallow vs. Larger Depth of Field

3.    Focal Length

Focal length doesn’t affect depth of field as much as the previous two factors. Focal length refers to the lens and how much the photograph seems ‘magnified’. Telephoto lenses tend to produce photos with a shallower depth of field than wide angle lenses.