[argyllcms] Detecting monitor black and white "blind" zones (dispcal)
- From: Іван Циба <ivantsyba@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 24 Apr 2011 15:52:31 +0300
Hi.
Every display (expressively ones with declared insane "contrast" ratio
of several thousands to one) have blind zones near white and black in
his reproduction curve. In this zones changing of signal did not
changes actual brightness on the screen (eg 0 0 0 and 5 5 5 both
visualising on screen as black with 0.6 cd/m2 which indicates that
display is not good at that brightness/contrast control position).
I propose add to dispcal interactive display adjustments menu two new
entries: "Black point quality" and "White point quality" (or add their
fuctionality to exist tools). That tools will be detecting whether
achieved blind zone or not (near white or black respectively), and
guide user to increase or decrease brightness or contrast of display
to drive out display reproduction curve from that zones.
I propose next algorithm for detecting blind zone:
1. set patch color (signal) to 0 0 0 (255 255 255 for white point).
2. measure brightness
3. set patch color to 13 13 13 (242 242 242 for white point) - That
values is used by GretagMacbeth iMatch 3 software that checks display
blind zones during calibration.
4. measure brightness
5. compare brightness measured in 2. and 4. steps
6. if brightness difference is too low, print "Increase (or degrease,
in white point adjustments) display brightness" (or contrast in CRT
display during white point adjustments)
7. if brightness difference is normal (in deltaE or in something
other) print "No blind zone detected, press space to continue".
8. goto step 1 or exit when space is pressed
Maybe "blind" is not good term, but I cant find better translation.
Sorry for my English
Thanks
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