Joseph Tainter <[EMAIL PROTECTED]> wrote: >"> I have been warned by some dSLR enthusiasts (among them the guy >mentioned here: >http://www.dpreview.com/news/0307/03070801nikkor1224review.asp) > >that some of my lenses, especially zoom lenses, may not be good enough > >to use on a digital SLR, even if they are quite good with my current > >cameras." > >Could someone explain why some existing lenses may not be "good enough" >to use with a digital slr? Many of us are waiting for the right digital >slr precisely so we can use our existing lenses with it.
In the simplest terms: The sensors of DSLRs are generally smaller than full-frame 35mm format (commonly by a factor of 1.5 - hence the 1.5x focal length "multiplication" effect). Thus you need to enlarge an image 1.5 times as much for a given print size. Therefore your lens must have 1.5 times higher resolution for equal quality at a given print size. Apparently this has caught quite a few people by surprise: There have been people who found that their "so-so" quality lenses that gave decent (but not great) performance on their film cameras simply didn't cut it on their DSLRs. The 1.5x greater enlargement necessary showed up the deficiencies of the lenses that went unnoticed at the lesser magnification necessary when making prints from film. If your DSLR effectively multiplies your focal length by 1.5, it also *divides* the lens' resolution by 1.5. So you'll want to use top-notch lenses whenever possible. I think the 31mm f/1.8 Limited would make a fine normal lens for the *ist-D, though! -- Mark Roberts Photography and writing www.robertstech.com
