View Full Version : Focusing a 42" Red Dot Artar

Lester Ferdinand
15-Jan-2001, 21:50
Okay, okay, I'm building a camera for this lens (I haven't bought the Winnebago for it yet)and I would like to ask if any one knows what is accepted as the dist ance for infinity focus? I'm asking how far into the landscape would the lens b e focused, not the distance from the film plane. The camera is going to be a 16x 20. This is so I can calculate the lenght of the focusing track.


Glenn Kroeger
16-Jan-2001, 00:15

Air Force test charts were focused at 50:1 so that's about 2100 inches or 175 feet. Many lenses are tested at 20:1 as a substitute for infinity.

adam friedberg
16-Jan-2001, 00:41
i'm not sure i understand the question. infinity focus is just that - the lens is one focal length from the film plane (42") and the lens will be focussed on infinity. but you are asking how far into the landscape the lens would be focussed. do you want to know the hyperfocal distance or what the near focus would be if focussed on infinity? if you want to calculate the focussing track should you then be more concerned with the highest reproduction ratio you plan to achieve? it could be lack of sleep keeping me from understanding what may be a simple question but now i'd like to know.