What is depth of field in photography, and how do you control it?
There are many terms which relate to a shallow or large depth of field in photography and photographers will bandy about these terms such as “hyperfocal distance”, “creamy bokeh”, “shooting wide open”, “background blur”, “subject separation”, or “zone of focus”.
The question is, what exactly is depth of field?
Depth of field simply describes how much of your photograph is in focus in its most important and basic sense. A large depth of field would make sure that in a landscape shot everything from the trees all the way back to the mountains would be in focus if you were to shoot a landscape image of forest and mountains, that is.
By contrast, a shallow depth of field would leave a background of trees and mountains out of focus if there was a subject whose facial features needed to be in focus in the foreground if we are shooting a portrait in that same location.
Exactly how deep the field of focus within an image is is always described by and referred to as depth of field. This field will roughly extend from one third in front of your focal point to two thirds behind it no matter how shallow or large it is.
A number of photographic means can be used to manipulate this. Changing aperture directly affects depth of field: using a small aperture, which is a large f-number like f/16, will produce a large depth of field – ideal for shooting a landscape where you want as much of the scene in focus as possible.
For a shallow depth of field you would be using a large aperture, such as a small f-number like f/1.8 – perfect for portraits, where you want the subject in focus but the background blurred. When someone shoots “wide open”, they’re usually shooting at a lens’ maximum aperture to create the shallowest depth of field possible (to get the blurriest background).
Depth of field is also controlled by focal length. A shallower depth of field is produced by shooting a portrait with a 135mm lens, thanks to its narrower field of view and greater magnification, than a 35mm lens shot with the same composition.
Depth of field is also affected by sensor size as well. With a crop sensor camera, you need to multiply the aperture by the crop factor to get the equivalent aperture in 35mm terms. Therefore with a Micro Four Thirds camera, which has a 2x crop factor, shooting at f/2 is actually shooting at an equivalent aperture – and an equivalent depth of field – of f/4.
Creative choice is what ultimately affects the depth of field. Landscapes don’t have to be sharp from front to back just as much as portraits don’t need to have blurry backgrounds. There really is no right or wrong way to use it so long as your subject is within your depth of field and is sharp.
Words by Elijah (Content Marketer) via Digital Camera World.