Well, 2:1 is about right for 35mm and 6x7. Since medium format covers everything from 6x4.5 to 6x17, that's a rather restrictive ratio.

The depth of field of any focal length is a function of the aperture, the focal length, and the distance of the plane of focus. If you could mount a 110mm Mamiya lens on your Nikon the depth is the same.

This ignores the effect of enlargement and choice of circle of confusion in different formats, but you can assume that DoF is less in practice rather than more!

DoF in medium format *is* much less than 35mm.

By shreepad joglekar on Saturday, January 04, 2003 - 10:30 am:

Hi all,
I understand that the focal lengths and the resultant equivalent views between medium format and 35mm lenses have a ratio of 2:1, so a 110mm Mamiya lens is same as 55 mm Nikon lense. My question is- how the depth of field varies in these two types of lenses?
Like the depth of field at F8 through a 35mm lens focused at a particular distance be same-less-more than that of the equivalent medium format lens at same f no and focused at the same distance