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Article #75

Re: What is the correct gamma value?

#75
From: 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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Message-ID: <1992Dec31.104748.17242@odin.corp.sgi.com>
Path: arc1-ca.pugleaf.net!sparky!uunet!spool.mu.edu!sdd.hp.com!sgiblab!sgigate!odin!blythe
References: <1992Dec22.230429.19706@uc.msc.edu>

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Path: arc1-ca.pugleaf.net!sparky!uunet!spool.mu.edu!sdd.hp.com!sgiblab!sgigate!odin!blythe
From: blythe@sgi.com (David Blythe)
Subject: Re: What is the correct gamma value?
Message-ID: <1992Dec31.104748.17242@odin.corp.sgi.com>
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Organization: Silicon Graphics, Inc., Mountain View, CA
References: <1992Dec22.230429.19706@uc.msc.edu>
Date: Thu, 31 Dec 1992 10:47:48 GMT
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