Godfrey DiGiorgi <[EMAIL PROTECTED]> wrote: >On Aug 29, 2005, at 2:18 PM, Mark Roberts wrote: > >>> The Medium Format solution may be to Pentax' advantage. >>> If 35 lenses don't have a good enough angle for straight-enough >>> sensor coverage, medium format lenses certainly do! >> >> I'm convince the "angle of incidence" stuff is BS. > >It's not BS, it's just not as big an issue as many seemed hysterical >to present it as. It becomes an issue when working with short focal >length lenses and a large sensor, and contributes to chromatic >aberration, mosaicing, and blooming problems at the edge/corner >regions of the frame.
Why only with short focal length lenses? (Since on an SLR they're retrofocus designs, they don't have a more severe angle of incidence at the edges of the sensor than normal lenses.) Canon's EF-S lenses move the optics *closer* to the sensor, making an EF-S lens reach the edges of an APS-C sensor at a greater angle than a standard lens on a full-frame sensor. Yes, wide angle lenses are more difficult to design for sharpness at the edges than normal lenses and digital sensors may manifest problems differently than film, but the angle business was invented on Usenet and isn't mentioned in any CCD data sheet I've ever seen (and, man, that took some reading: These kinds of "data sheets" are 100-or-more-page novels!) -- Mark Roberts Photography and writing www.robertstech.com
