Archived posting to the Leica Users Group, 2003/04/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> Sounds like we're going to need an experiment to learn the truth here. I > did some cursory tests similar to what Clive describes, which bear out my > opinion on this. I will try to whip up something tomorrow to post for > review. A digital camera with a smaller than 24x36 frame does > *not* change > the lens' focal length. It merely crops the image projected by that lens. > DOF and perspective are the same as they would be on a full-frame camera, > but the image is cropped. > > --Jim > It does, however, change the "effective" type of lens that you are using - that is, the actual used field of coverage changes and the exact same lens can go from being a telephoto to a wide angle. This is all old hat to anyone who uses two different large format cameras. One problem we are getting here is people using the same term to mean different things (and by this point in the discussion, I'm not quite sure what the question is anymore). On my 8"x10" camera my 210mm lens is a moderate wide angle lens (= to say around 28mm on 35mm cameras) Now, if I take that EXACT SAME lens and put it on my 4x5 camera it becomes a moderate long/telephoto lens ( = to around 75mm or so on 35mm cameras). But you are also right the DOF from use on one format camera to another has not changed, nor has the focal length of the camera - I still need 210mm of bellows from the ground glass to the lens to focus at infinity on either camera. But on 4x5 I am seeing a much wider (and higher) part of the scene than on the 8x10. Your lens can "effectively" change from being a telephoto to a wide angle lens, but nothing else has changed apart from the actual field of view that it covers 'on that particular format'. >Sounds like we're going to need an experiment to learn the truth here. No-one needs to do any experiments here to learn the truth (unless you want to invent the wheel again...) - just read a couple of basic books are articles in using lenses on different format large format cameras - people did all the experimenting for you about 100 years or so ago :-) tim PS - trying to read the threads on this I think there are about three different questions being asked and being answered at the same time... so I'm probably answering a question no one is asking - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html