> > and the profile applied the gamma is 2.24 again! This seems to indicate > > that dispcal is creating a calibration curve with a low gamma and then > > "profile" is compensating and setting the gamma higher again. > > A profile doesn't (in itself) change anything - it's just a > characterization of the device. Any change you see in applying > a profile is the combination of two profiles, the source and > destination profile. So a change in gamma will be the effect of > the comparative gamma between the two profiles, and the source > profile gamma may not be a simple power curve (ie. sRGB), and > will have different black end aim points, the effect of which will > depend on the linking intent etc. The source profile in my tests is sRGB - gamma 2.2 (or close) isn't it? So sRGB converting to Monitor profile (perceptual) should not involve a gamma change, yet images noticeably darken when I apply the profile conversion. > The target curve takes into consideration the offset needed in > the black point, to achieve the black point target chromaticity. > For a CRT this usually isn't much, and the approximate gamma > should match the aim curve reasonable well. For an LCD with -k1.0, > this may be quite an offset, causing a noticeable discrepancy, and > a loss of contrast. (If you calibrate with -v, the Gamma curve > offset value is reported, so you could check how much it changes > between -k1 and -k0) > You could try calibrating with -k0.0, and see if the approximate > gamma is now in better alignment with the target one, and your contrast > ratio is better. I've made the -k0.0 behaviour the default for LCD's > in future versions, since I suspect this is what will work best as > a default. I'm getting the same results with -k0 and -k1; resulting callibration curve gamma is 2.05, not 2.2. Below I've listed the output from dispcal -E for .cal files with k=0 and k=1. The gamma offset is the same (~0.08) in both cases. I don't understand why the gamma offset is low yet the gamma seems so far off. Here's the output from dispcal -E on a .cal file with a k of 1: I:\Util\Argyll\profiles>..\bin\dispwin -d2 t42pk1.cal I:\Util\Argyll\profiles>..\bin\dispcal -v -d2 -yl -E Setting up the instrument Place instrument on test window. Hit Esc to give up, any other key to continue: Display type is LCD Target white = native white Target brightness = native brightness Target gamma = 2.200000 Commencing device calibration patch 6 of 6 Black = XYZ 0.46 0.48 0.48 Red = XYZ 59.73 35.03 6.86 Green = XYZ 48.17 81.70 17.92 Blue = XYZ 22.29 21.10 100.81 White = XYZ 128.15 135.69 123.06 Initial native brightness target = 135.690000 cd/m^2 Target white value is XYZ 128.150000 135.690000 123.060000 Target black point = 0.489440 0.518237 0.470000 Gamma curve offset = 0.079598 patch 100 of 100 Verification results: Brightness error = 0.030000 cd/m^2 White point error = 0.021150 deltaE Maximum neutral error (@ 0.095629) = 1.150478 deltaE Average neutral error = 0.447931 deltaE The instrument can be removed from the screen. Here's the output from dispcal -E on a .cal file with a k of 0: I:\Util\Argyll\profiles>..\bin\dispwin -d2 t42pk0.cal I:\Util\Argyll\profiles>..\bin\dispcal -v -d2 -yl -E Setting up the instrument Place instrument on test window. Hit Esc to give up, any other key to continue: Display type is LCD Target white = native white Target brightness = native brightness Target gamma = 2.200000 Commencing device calibration patch 6 of 6 Black = XYZ 0.32 0.33 0.46 Red = XYZ 59.62 34.87 6.85 Green = XYZ 48.05 81.59 17.93 Blue = XYZ 22.10 20.88 100.79 White = XYZ 128.06 135.58 123.05 Initial native brightness target = 135.580000 cd/m^2 Target white value is XYZ 128.060000 135.580000 123.050000 Target black point = 0.468322 0.495823 0.450000 Gamma curve offset = 0.078043 patch 100 of 100 Verification results: Brightness error = 0.110000 cd/m^2 White point error = 0.059313 deltaE Maximum neutral error (@ 0.112249) = 6.966823 deltaE Average neutral error = 3.416810 deltaE The instrument can be removed from the screen.