What is the correct gamma value?

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2 total messages Started by Wes Barris Tue, 22 Dec 1992 23:04

#55

Author: Wes Barris
Date: Tue, 22 Dec 1992 23:04

24 lines
1350 bytes

The man page for gamcal says:

   "Normally the gamma of the display should be set to
    2.4 using the program /usr/sbin/gamma."

However, the following lines are found in /usr/lib/X11/xdm:

   Xlogin:glGammaDefault="1.7"
   Xstartup:glGammaDefault="1.7"

NOTE: These files (Xlogin and Xstartup) do not seem to be setting the gamma
      anyway but that is a separate issue.


Using the gamcal program to help calibrate the gamma leads me to believe
that 2.4 is the "correct" value.

I am running IRIX 4.0.5 on a 4D/35.  Is there a reason for the two
different gamma values found on my system?


===============================================================================
Wes Barris                                                   PH: (612) 626-8090
Minnesota Supercomputer Center, Inc.                         Email: wes@msc.edu

Re: What is the correct gamma value?

#75

Author: David Blythe
Date: Thu, 31 Dec 1992 10:47

35 lines
1937 bytes

In article <1992Dec22.230429.19706@uc.msc.edu> wes@msc.edu writes:
>The man page for gamcal says:
>
>   "Normally the gamma of the display should be set to
>    2.4 using the program /usr/sbin/gamma."
>
>However, the following lines are found in /usr/lib/X11/xdm:
>
>   Xlogin:glGammaDefault="1.7"
>   Xstartup:glGammaDefault="1.7"
>
>NOTE: These files (Xlogin and Xstartup) do not seem to be setting the gamma
>      anyway but that is a separate issue.
>
>
>Using the gamcal program to help calibrate the gamma leads me to believe
>that 2.4 is the "correct" value.
>
>I am running IRIX 4.0.5 on a 4D/35.  Is there a reason for the two
>different gamma values found on my system?

the correct gamma value is theoretically a property of the monitor (CRT
and associated electronics).  gamcal will help you determine what this
value should be.  In practice asthetics, religious beliefs, the application
itself, etc,  perturb this value.  I believe the two values you have seen
reflect two different opinions of SGI engineers (I think they bracket the
typical range of values).  I believe 1.7 is the installed default regardless
of the monitor shipped with the system.
	-db

>
>
>===============================================================================
>Wes Barris                                                   PH: (612) 626-8090
>Minnesota Supercomputer Center, Inc.                         Email: wes@msc.edu

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