Archived posting to the Leica Users Group, 2006/11/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Lee I am glad someone finally got to those pesky old circles of confusion. They were invented to confuse a whole circle of photographers at one time and they do. :-) Walt Lee Wai Leong wrote: >Just to add. I mentioned that the industry had generally used a CoC of 0.03 >mm for 35 mm lenses. > > How is this 0.03 mm derived? > > As mentioned in Wikipedia, using the so-called ?Zeiss formula? the circle > of confusion is sometimes calculated as d/1730 where d is the diagonal > measure of the original image (the camera format). For full-frame 35 mm > format (24 mm ? 36 mm, 43 mm diagonal) this comes out to be 0.024 mm. > > A more widely used CoC is d/1500, or 0.029 mm for full-frame 35 mm > format, which corresponds to resolving 5 lines per millimeter on a print > of 30 cm diagonal. Values of 0.030 mm and 0.033 mm are also common for > full-frame 35 mm format. > > Since d is smaller for a digital sensor that is less than 24x36 mm, it is > clear that a 35 mm lens used with a digital sensor must have a smaller DOF > at all distances. > > Hence, the DOF markings now on our Leica lenses are no longer correct > when you put them to use on the M8. > > Send instant messages to your online friends http://uk.messenger.yahoo.com > >_______________________________________________ >Leica Users Group. >See http://leica-users.org/mailman/listinfo/lug for more information > > >