Archived posting to the Leica Users Group, 2006/11/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]"I'm not shure about that. Yes, the DOF marks on the lenses are no longer correct when used with a M8 - but the other way round." For the same lens, the same focus distance-- assume that the subject at distance X is in focus. The DOF markings extend from X-a to X+b. Hence, at X-a, the CoC is 0.03. Similarly, at X+b, the CoC is 0.03. Since the formula states d/1500, the CoC on a digital sensor smaller than 24x36 mm is less than 0.03. Say 0.02. Obviously, if X-a and X+b have a 0.03 CoC, then to get a CoC 0.02 the DOF markings for the digital sensor must be inside X-a and X+b. Hence the digital sensor creates a smaller DOF. "I don't make any calculations - am not really interested in the mathematical aspects of photography - but a few months ago I did just a few empiric tests with the same 50mm/1.2 lens wide open on a M6 and a R-D1 (with it's crop factor of 1,5). It seems to be the opposite - on the R-D1 shots there was visibly more DOF. Same lens/smaller format = MORE DOF." I think it's likely you shot the same subject from different distance, due to the crop factor. But it is true that smaller lenses and smaller formats have larger DOF's. That's why digicams have almost everything in focus. That's due to their effective focal length, which is something like 7 mm. Lee Wai Leong "And if you play golf, you're my friend..." Send instant messages to your online friends http://uk.messenger.yahoo.com