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| p.4 #5 · p.4 #5 · Canon EF 24-70mm f/4L IS Resolution Tests! |
Jim, that's an excellent point about resolution loss with distortion correction. I'm going to see if I can figure out a way to do that.
I'd start with multiple images of the USAF resolution target core in edge and corner positions, and then compare computed resolution for pre- and post- distortion correction, using Canon lens profiles in CS PS6. That part would take time, but it could be done. OTOH, I haven't figured out how to get my hands on multiple copies of the lenses in question, without quickly wearing out my welcome at CPS Canada.
I had a fellow today who'd bought a Nikon 16-35 f/4 VR (AKA the Nikon Fisheye Zoom) from us screaming about the horribly soft corners at 16mm. He sent it back, I tested it twice and it was superb. Turns out he was correcting that 6% barrel distortion and then evaluating the corners, which did, indeed, then suck .