Depth of Field in Photography 2

Depth of field can be a daunting term to get to grips with, but is actually a very simple concept to understand. Use it to take your photos to a new level.

Depth of field refers to the area of a scene which appears focussed. It is a product of three factors - the lens aperture, the focal length, and how far from the subject we are. This article covers these three factors and looks at how we can use them to control depth of field in our photography.

 

What is Depth of Field?

 

When we adjust our camera's lens to focus on a subject it will only achieve perfect focus at one particular distance; anything in front or behind this point will be blurred to a greater or lesser degree.

 

What Affects Depth of Field?

Depth of field is affected by three main factors:

• Lens aperture diameter
• Focal length
• Distance from the subject

 

Aperture and Depth of Field

The aperture determines the diameter of the beam of light that the lens admits. The wider the aperture, the wider the beam of light. A wider beam is more susceptible to depth of field effects than a narrower beam.
Using a wider aperture produces a shallower depth of field; using a narrower aperture gives a greater depth of field.

 

Focal Length and Depth of Field

Focal length is a measure of how much the lens magnifies a scene. The lens also magnifies differences in focus.
A longer focal length magnifies focus differences, resulting in a shallower depth of field.

 

Focus Distance and Depth of Field

The closer the subject is to the camera, the greater the relative distance from the front to the back of that object. A high relative distance gives a corresponding reduction in how much of the object appears in focus.

 

Controlling Depth of Field

However, this is usually unnecessary, and you can achieve the results you want much more easily by applying the following rules of thumb:

To Increase Depth of Field	To Decrease Depth of Field
Narrower aperture	Wider aperture
Shorter focal length	Longer focal length
Move away from subject	Move towards subject

Info: Pete Williams