I agree it is not a definitive comparison, Paul. Unless I have a DA12-24 to test against, I can't do much of a comparison test. ;-)
I did a reasonably exhaustive set of test exposures with the DA14 over the entire range of apertures and at various focus distance settings, tripod mounted, and that's what the body of my comments is characterizing. Chromatic aberration normally varies based on the angle of the light path off the lens axis in a constant manner (to first order approximation). Much like rectilinear correction, although some modern zooms have so many elements with spherical and aspherical shapes that the rectilinear aberrations propagate in waves like slices through a XsinX function. There's variation based on aperture setting as well, of course. The incidence angle of the light intercepted by the lens is a much lower order effect. With the DA14 at f/5.6 to f/8, I find I get a pretty effective reduction to zero CA if I set Red/Cyan to -26 and Blue/Yellow to +19. With the DA12-24 samples I saw, it required values for the 12 and 18 mm sample shots taken at f/8 at -43/+28 respectively. Godfrey On Mar 25, 2007, at 4:44 PM, Paul Stenquist wrote: > But it's not definitive. The DA 12-24 samples were mine, and they > were hand held. CA is dependent very much on the angle of the light. > I would be surprised if the DA 14 were not better at 14mm than the DA > 12-24, but I wouldn't jump to any conclusions based on what you've > read here. > Paul > On Mar 25, 2007, at 7:07 PM, Jack Davis wrote: > >> Thanks, Godfrey. Exactly the sort of information I had in mind. >> Detailed and meaty. >> Considerate of you to take the time. :) >> >> [snip] -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
