Camera Basics: Depth of Field

A wide aperture gives you a narrow depth of field.

For instance, at f/2.8, your camera lens is wide open. It allows the camera to shoot at a faster shutter speed.

How does it affect your photo? If you want to isolate a small part of a flower, you shoot at f/2.8. Only a small portion of the flower will be sharp, and the rest will be blurred as the background.

This is very useful in macro photography.

In comparison, at f/22 (a smallest aperture or depth of field for most lenses), a lens takes longer time to absorb the light, therefore it requires slower shutter speed and longer exposure. However, it will make the details of almost every part of the photo sharp.

Traditionally some well-known landscape photographers including Ansel Adams, liked to shoot at very small depth of field. He was a part of the well-known Group f/64. His photos are famous for very sharp details.

Please take a look at the sample photos at different apertures. The photos were taken on tripod to avoid blurry which may be due to camera shake.

Nowadays, most digital camera lenses only gives you f/22 as the smallest depth of field.

The optimal depth of field is usually around f/5.6-f11. However it varies for each lens.

[Revision: Two more photos have been added to compare the details at different apertures. - July 16, 2010]

In theory, a smaller depth of field, such as at f/22, should make a photo sharp from corner to corner. In reality, it is not likely to be the case. The reason is, if you are shooting at a smaller aperture, the resolution (which affects the sharpness of your photo) will be limited by the diffraction of your lens. It will make the photo unsharp at the corners. However, lens diffraction is highly technical and beyond the scope of this topic.