I actually discovered that XSane can do the gamma correction in software. However you have to manually uncheck a box. It should automatically detect it cannot send a gamma table, but fails. Is it the mistake of XSane or of the driver?
On Sat, May 22, 2010 at 6:35 PM, Valentin David <valentin.david at gmail.com> wrote: > I had troubles making the gamma correction to work in transparency > unit mode on my Canon 8800F. Since the problem appeared both on > xscanimage and XSane, I thought it was probably the driver. So I > looked the driver source, and understood that in TPU, the scanner does > not get any gamma table but rather sends 48 bits data. > > I also discovered that it was using a gamma table in flatbed mode. I > tried, and then it does work. Which confirms the thing. > > This is great to get raw data. However it seems that the gui frontends > do not tell you cannot set a table. And also, I cannot use GIMP > directly. On underexposed or overexposed films, I get quantization > artifacts. I need to reinstall CinePaint. :( > > In XSane, the color correction also gets strange. I do not know if it > is related. The red looks overexposed, green OK, and blue under > exposed. > > Certainly the driver needs to say if the gamma correction will be done > or not. And the frontend should apply it on its own if there is no > correction done. At least for the user not to get this unexpected > behavior. > > -- > Valentin David > valentin.david at gmail.com > -- Valentin David valentin.david at gmail.com
