Archived posting to the Leica Users Group, 2008/12/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Aram wrote: I would think the film vs. sensor would also effect SLR's, since focusing is not on the film itself. But shouldn't the focus shift as you stop a lens down also effect an SLR? I am assuming that the SLR focuses (auto or manual) with the lens wide open, then stops the lens down to take the photo. So, this should have the same effect as say focusing accurately on a rangefinder for whatever aperture the coupling is accurate, then taking the picture at some different aperture? Does this sound right, or is my retired brain not working correctly? Yes, absolutely. An SLR focuses with the lens wide open and then stops down to take the photo with the focus locked in position. Focus shift will cause problems for these cameras too. The Canon EF 50/1.2, a very accomplished design with a moulded aspherical element, has considerable focus shift. Canon could have ameliorated this by also including a floating element, but they probably figured that the price was already high enough. This has really upset some people, for example: http://www.kareldonk.com/karel/2008/07/16/canon-ef-50mm-f12-l-defective-by-design/ With an autofocus camera and a chipped lens, manufacturers, however, have an unusual opportunity that has not yet been capitalised on. It would be easy enough to design the system so that once the camera has recognised the lens, it is also programmed to adjust for focus shift according to what aperture has been set. The only camera to date with such a system, however, was the Konica Hexar AF (not the RF). Marty Gallery: http://gallery.leica-users.org/v/freakscene -- Be Yourself @ mail.com! Choose From 200+ Email Addresses Get a Free Account at www.mail.com