Quote Originally Posted by wiltw View Post
Jim Jones actually was correct...50mm lens (2.1* frame height) on 135 format at f/2 focused at 100' has DOF zone of about 200'; 190mm lens (2.1* frame height) on 4x5 sheetfilm at f/8 focused at 100' also has DOF zone of about 200' !!!

It is just that most folks think of 'lens of same angle of view' at 'same f/stop', rather than at 'same aperture diameter (in mm)', when they shoot.

The comparison of 'DOF zone' is a rather simplistic comparison, however, as there is no consider of how OUT OF FOCUS the background will be, and that is related to the FL (greater FL = greater blur of the distant out-of-focus background)
Right. Just talking about practical application of what Jim said. That is, DoF of a 100mm lens at 2.8 is the same whether it is on a 35mm camera or a 6x7 camera. But the 100mm on 6x7 is the 'normal' lens, while a 50mm on the 35mm camera is the 'normal'. So for equivalent FoV the 35mm camera will have greater DoF at a given f/stop. And that's what people should understand, not just that "35mm has more DoF".