Steve Yeatts wrote:
Is there a formula to calculate the required distance between the lens board
and the film plane for an object at a given distance from the camera?
Thanks in advance.

If u is the distance from the lens to the subject, v the distance of the
lens from the film plane, and f the focal length, then

1/u + 1/v = 1/f.

So

v = fu/(u - f)

In words, multiply the subject distance by the focal length, and then
divide that by the difference between the subject distance and the focal
length.

But this requires some additional qualification since the lens has an
extent of its own. The subject distance is measured from a point called
the front principal point and the film distance is measured from a point
called the rear principal point. For most lenses, these points are both
close to the center of the lens which in turn is close to the lens
board. But for lenses of telephoto design, both these points may be far
in front of the lens. For many wide angle lenses, the rear principal
point is a short distance in back of the lens board. Usually lens
specifications tell you what the rear flange focal length is. If you
know that and the focal length, you can determine the position of the
rear principal point.


Steve (new to 4x5)