Not sure I am the best person to explain adding the GL curve as I am a rank amateur with QTR. I am a trial-and-error kinda guy, just kept tweaking the curve until I got what I wanted. I have posted one of my QIDF files and a screen shot of the dialog at: http://appce.com/mail/QTR.zip You may be able to open the QIDF file in Curve Creator; I use the Windows version, don't know if Mac is the same. BTW, this curve gives a very high contrast print on my R1900.