Graeme, I took your advice and calculated the gamma from 3 readings taken with "spotread" at 64, 127, and 191. The results are interesting and you can see them in the link below: http://spreadsheets.google.com/pub?key=pL40582sXA94lQ4iLfbf5Ww The spreadsheet is sorted by the "Error" column, which is calculated as: (2.2 - G at 64)^2 + (2.2 - G at 127)^2 + (2.2 - G at 191)^2 The gamma is calculated as a truncated ideal gamma curve (ignoring black point). As expected, the difference between the measured gamma and gamma 2.2 is lowest when the calibration curve and its corresponding profile is applied. The next most accurate is the uncalibrated display (a Thinkpad T42p with Flexview 1600x1200 screen). Next most accurate is the calibration curve from when dispcal is run with -g2.6, then when dispcal is run with -gs or -g2.4, and lastly when dispcal is run with -g2.2. Can you check my results and if they look ok, doesn't this indicate significant error in the generation of the calibration curve for g2.2? I can give you access to the original active spreadsheet (instead of the static page above) if you want to look at it in more detail. I'll need your Google mail address to share it. - Bill