Posted by carol whitehill on November 06, 2000 at 22:09:17:
In Reply to: Re: lens for 1:1 shooting pacemaker speed posted by Les on November 06, 2000 at 08:17:21:: A 135mm lens should give you a 1:1 on a 4x5 pacemaker, actually slighty more.
: If the magnification isn't critical then rack the lens past the infinity stops to the front of the bed, then rack the focus until the belows are reasonably tight. Now open the lens and focus by moving the camera toward/away from the subject.
: Unless you are judging exposure by Polaroid, be sure to add 2 to 2.5 stops to the meter reading to account for the bellows factor*.
: *The f-stop is a quotient. the diameter of the aperture can be divided into the focal length of the lens f times.(a 10mm hole can be divided into a 160mm lens 16 times, thus f16)
: However the distance between the lens and the film plane is equal to the focal length only when focused at infinity. You will find all lenses focus at 1:1 at twice their focal length, so now this 10mm hole has to be divided into 320mm, and we come up with f32 or two stops slower than normal.