BTW, in Lightroom, setting a lens vignetting preset to +55 on amount and 14 on midpoint completely eliminates the falloff.
see: <http://homepage.mac.com/godders/DAstar_50-135-falloff- correction.jpg> Godfrey On Nov 7, 2007, at 2:36 PM, Godfrey DiGiorgi wrote: > Photoshop shows values based on [EMAIL PROTECTED] 127 is the mid > point, and it's about 25.5 points per EV step for the full range > from Zone 1 to Zone 10. So 130 is right around Zone V and 80 is > right around the boundary between Zone 3-4, so it looks like you > are showing about 1.5-2 steps light falloff from center to edge > wide open, a rough first order approximation. > > (Lightroom shows it to be about 51% brightness on center and 32% at > corners, again showing a little less than 2 steps falloff to the > corners. 10% on grayscale value is 1 step in Lightroom's scale.) > > Godfrey > > On Nov 7, 2007, at 1:53 PM, Dario Bonazza wrote: > >> Hi folks, >> >> Here is a white-wall shot taken with the DA* 50-135 @ 135mm F2.8, >> where it >> shows its highest light falloff at corners: >> www.dariobonazza.com/public/Vignetting.jpg >> >> Do yo have any idea about how to measure that? I mean, how to >> translate >> Photoshop values (around 130 for each RGB channel at center, >> around 80 at >> corners) into f/stops? >> >> Thanks to anybody enlightening me ;-) > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
