[argyllcms] brightness scaled down a lot

Hi all,

having given up on my two old CRTs, I'm trying to calibrate/profil my
laptop's display. As a noob, I've only recently noticed how the
difference between pics on screen and the printout were not because of
the photo lab doing smth. wrong but because my TFT was too bright.

So, I'm trying to limit brightness but find that I always end with a
display calibrated to a brightness way lower than the one I picked.



> # ./dispcal     -v     -d1     -c1  0731707317073,0.251984126984,1.0     -ql  
>    -m     -t5000     -b100         -f0     -k0 bla
> XRandR 1.2 is faulty - falling back to older extensions
> Setting up the instrument
> Place instrument on test window.
> Hit Esc, ^C or Q to give up, any other key to continue:
> Display type is LCD
> Target white = 5000.000000 degrees kelvin Daylight spectrum
> Target white brightness = 100.000000 cd/m^2
> Target black brightness = native brightness
> Target advertised gamma = 2.400000
> Commencing device calibration
> patch 6 of 6
> Black = XYZ   0.45   0.57   0.93
> Red   = XYZ  37.58  30.98   5.52
> Green = XYZ  32.23  70.24  17.04
> Blue  = XYZ  21.13  22.89 102.57
> White = XYZ  90.10 123.03 123.27
> patch 48 of 48
> Had to scale brightness from 100.000000 to 53.011488 to fit within gamut,

Suppose this is the culprit?
Is there way to do the math to see what input params will give me a
brightness of around 100?

> corresponding to RGB 1.000000 0.557911 0.576598
> Target white value is XYZ 51.118411 53.011488 43.717743
> Adjusted target black XYZ 0.44 0.57 0.93, Lab 9.55 -7.26 -11.28
> Target black after min adjust: XYZ 0.44 0.57 0.93, Lab 9.55 -7.26 -11.28
> Gamma curve input offset = 0.325443, output offset = 0.000000, power = 
> 4.043632


TIA,

Karl.

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