On Sun, 2004-02-08 at 20:07, Christopher Marshall wrote: > I have been using Sane for about two months now with a CanoScan LiDE 80 and > getting great results. > > I have been wondering, however, about how best to enhance my images after > scanning. > > They have been coming out fairly dark with no corrections. I have dealt with > this in two ways. > > For scanning text documents, I set the backend --contrast argument to 30 and > have no complaints. > > For photographs, however, setting --contrast to 30 is a poor choice compared > to using the GIMP to > brighten the midtones with the image->color->curves tool. I add a control > point in the middle of > the "value" curve and move it up and to the right and the image gets very > close to the original > with this. However, I can still see differences in the colors when comparing > the image on the > screen to the photo I scanned. > > I just read up on gamma correction and it has hit me that I was approximating > a gamma correction > the way I was using the gimp curves tool in the value channel. > > So what I am wondering is this. What is a reasonable procedure for figuring > out a good gamma > correction to give to the backend when scanning photographs? > > Might it make sense to print a test page with solid blocks of red, blue, and > green colors spread > across the 0,255 range, scan that page with sane, and then use the Gimp to > get the exact values > of the colors, then calculate the best gamma correction from that? > > Has anyone ever done this? > > Chris Marshall
Calibration your scanner with a scanner calibration target see for example http://www.targets.coloraid.de/ Example for profiler program see http://www.littlecms.com/profilers.htm -- ---------- m.vr.gr. Gerard Klaver
