[argyllcms] Re: Multiple issues with Argyll, please help

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 27 Aug 2008 14:20:58 +1000

Rajiv Mehra wrote:
Now while I have your attention, Graeme, what is the best way to prevent greyish blacks? even with this command........ 
dispcal -v -y c -q m -w 0.313,0.329 -g 709 -p 0.5,0.5,1.7 -f1 -k0 g70-1
......while watching movies after dispcal......fade to black scenes have elevated brightness. Also, the overall image lacks "punch" . I think it is reducing the contrast/brightness to correct the greyscale or something. 

If you are aiming for a non-native white point, then it will reduce
the maximum brightness, since channel values can only be reduced
from white. so try it without -w 0.313,0.329.

I'd be leaving -f alone (ie. not using -f1) unless you've determined
specifically that it gives you the results you want, since -f1 will
give a steep target curve that may reduce shadow detail near a non-zero black.

Note that inaccuracies in the instrument reading very low levels
may lead to a black that isn't quite as black as it should be,
although the i1d2 isn't too bad in that regard compared to
the Huey or Spyder2. The Eye-One Pro is probably better, as is
the DTP92 and DTP94.

Please note that since you're using -g 709, that you need to
use ambient compensation to get the desired subjective result,
or instead you should be using a gamma of 2.4, since this
is what Rec 709 TV encoded images are assumed to be displayed on
in a darkened viewing environment.

Since you seem to be aiming for a subjective rather than technical
calibration, it's really up to you to figure out what works.

Graeme Gill.

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