[Leica] Depth of Field

[pearceww at rmi.net (Warren Pearce)]

Many years ago, I took part in a discussion on Depth of Field. I went 
to my physics/optics books and ran the equations as well as doing 
some actual shooting of pictures.

As a starting point, the Scheimpflug effect does not care about the 
camera!!! Tilting the film and lens is a significant advantage of a 
view camera. That was the reason I got a view camera a long time ago.

The following discussion is based on not being close to the 
hyperfocal distance for any of the lenses. The closer you are to the 
hyperfocal distance, the less the optical equations are exact.

If you change the lens focal length and then your distance to the 
subject so the image size on the film is the same, the depth of field 
will be the same for the same F-stop no matter what focal length you 
use. We always say that a wide angle lens has a larger depth of 
field. That is true because we are essentially saying that the image 
size for some object in the picture is smaller than if we used a 
longer lens and stayed in the same place. If we just went further 
away from the subject with out changing the lens, the depth of field 
around the subject would increase as the subject is now smaller. 
Again, if we are getting to where the hyperfocal distance is within 
our range/F-stop, then the optical  equations do not take that into account.

+=+=+=+=+=+=+=+=+=+=
Linda & Warren Pearce
Colorado Springs