-------- Original-Nachricht -------- > Datum: Wed, 31 Aug 2011 19:09:48 +1000 > Von: Graeme Gill <graeme@xxxxxxxxxxxxx> > An: argyllcms@xxxxxxxxxxxxx > Betreff: [argyllcms] Re: Faking the white point in camera calibration > Stephen T wrote: > > > Now, rather than editing the wtpt tag, maybe I can edit the .ti3 file > and then profile that? I > > am thinking to edit the XYZ_X XYZ_Y XYZ_Z and RGB_R RGB_G RGB_B data for > GS00 to make everything > > neutral. I can make the reference Lab neutral by setting a and b to > zero. Then I can convert > > these numbers to XYZ. For the camera, I can use the average of the > measured values and set > > R=G=B. > > > > Is this safe or would it make problems for colprof and screw up the > model fitting? > > That may work, as long as the change in the white patch is not too great. I'd tend to add a faked white patch with RGB_R=RGB_G=RGB_B=100 and "corresponding" XYZ numbers to the .ti3 file. It may be a bit problematic though to estimate the XYZ numbers of this patch, as this involves extrapolation and potentially even clipping (if a profile with CIELAB PCS is used for estimating the XYZ numbers from the RGB numbers with icclu). And if Y of the faked white patch happens to be greater than 100, then it may also be necessary to downscale/darken all XYZ numbers in the .ti3 file correspondingly. Regards, Gerhard -- Empfehlen Sie GMX DSL Ihren Freunden und Bekannten und wir belohnen Sie mit bis zu 50,- Euro! https://freundschaftswerbung.gmx.de