Last week I addressed the aperture’s effect on depth of field. This week, I’ll take it one step further and talk about a lens’s focal length and it’s affect on depth of field. As a general rule, we attribute great depth of field to wide angle lenses…
20mm @ f16
and, we think of telephotos as having very little depth of field…
1000mm @ f22
Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because we are normally shooting from a much greater distance to our subject than we would be with a wide angle lens. If the subject occupies the same area of the image for both lenses (standing far away and filling the frame with a telephoto and standing closer to fill the frame with a wide angle, the depth of field is almost the same!
Focal Length 10mm, Distance (m) .5, DOF (m) .482
Focal Length 20mm, Distance (m) 1.0, DOF (m) .421
Focal Length 50mm, Distance (m) 2.5, DOF (m) .406
Focal Length 100mm, Distance (m) 5.0, DOF (m) .404
Focal Length 200mm, Distance (m) 10, DOF (m) .404
Focal Length 400mm, Distance (m) 20, DOF (m) .404
(information from Cambridge Color)
So, while focal length plays a big role in DOF, I don’t usually select a lens based on the depth of field it will offer but, rather select the lens based on my subject and what I want to communicate in my images. I typically shoot my wide angle lenses closed down for greater depth of field…
20mm @ f16
and my telephoto lenses opened up fairly wide to minimize depth of field and make the subject pop…
600mm @ f4
Knowing the effect of the aperture and focal length I select enables me to control depth of field.
Stay tuned for more tips, tricks and techniques to control depth of field.
