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' !!!
Originally Posted by lxdude
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)