Thanks Dan,

Good point. I will start with my 150mm.

Quote Originally Posted by Dan Fromm View Post
Key magic formulas:

extension = focal length *(magnification + 1)

Extension is measured from the film plane to the lens' rear node. For most LF lenses the rear node is close to the diaphragm.

Front node to subject distance = focal length *(magnification + 1)/magnification

For most LF lenses the front node is close to the diaphragm.

effective f/ number= f/ number set * (magnification + 1)

You're going to need 600 mm extension to shoot a 300 mm lens at 1:1. Front node to subject distance will also be 600 mm. There are some subjects for which that much working distance is helpful, but in general you'd be better off using a shorter lens at 1:1.