John Francis wrote: > On Sun, May 18, 2008 at 07:03:29PM -0400, Mark Roberts wrote: > >> John Francis wrote: >> >>> On Sat, May 17, 2008 at 08:23:22PM -0700, Bob Blakely wrote: >>> >>>> To do perspective correction in photoshop or any other imaging software, >>>> you >>>> must loose pixels, synthisize pixels or both. Shift is still the way for >>>> digital purists. >>>> >>> That's possibly true (but watch out for those loose pixels :-) >>> But unless you're printing on a device with native resolution that >>> exactly matches your original image, you're going to end up with >>> lost and/or synthesized pixels, anyway. >>> >> With a perspective shift lens you're using a larger-image-circle lens >> and those generally (though not always) have lower resolution than >> standard 35mm lenses. And by using the shift capability you are, by >> definition, using more of the edge of the image circle, which is >> virtually always lower resolution than the center. >> > > While that's true for a normal lens, it isn't necessarily so for a > shift lens - it gets the increased image circle by means of the shift. > If it doesn't have the larger image circle to begin with, all shift will do is show those limits. Having a shift cannot possibly increase the size of a lenses image circle. On the other hand tilting might appear to increase the size of the image circle, but it does not. Image circle is inherent in the lens design.
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