Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!usc!apple!radius!pierce
From: pierce@radius.com (Pierce T. Wetter III)
Newsgroups: comp.graphics
Subject: Re: Checking temp of a screen (was Re: HELP NEEDED IN PHOTGRAPHING SCREENS
Message-ID: <1401@radius.com>
Date: 29 Jan 91 18:32:10 GMT
References: <1991Jan27.232910.22575@ms.uky.edu> <1991Jan28.010515.708@vixvax.mgi.com> <1991Jan28.234755.22068@lavaca.uh.edu>
Lines: 45

>In article <1991Jan28.010515.708@vixvax.mgi.com> keeney@vixvax.mgi.com (Richard Keeney) writes:
>>Use a daylight balanced film - most CRT's are calibrated to have a white
>>of 5500 deg. K or so.

>How do I check this?  I'm trying to find some way to have our color
>images look the same from screen to screen.  I'd love to know how
>hot/cold they are so I can just say "gamma +.1 foo.r | display" or
>somesuch.


     Ahem.

    Most CRT's are calibrated to have a white temp of 9300K, to match
 white monochome displays. TV sets and the like are calibrated to 6500K.


   How to tell the temp of your screen:

     1: Buy a minolta TV color analyzer. This will tell you the chromaticity
        coordinates of the white, and you can compare this to a table to find
        the approximate color temp.

     2: Get a photometer or something that can measure brightness, and 
        measure the brightness of R,G &B. Look up the color coordinates of
        your phosphors, and solve for temp.

    


  How to solve your real problem matching two screens:

    1: if you have a macintosh, buy a radius PrecisionColor calibrator, and
       it will adjust your gamma corrections to match.

    2: Since you don't have a mac, as implied by your unix command above,
       take the backs off your monitor, get a screwdriver, and adjust the
       color balance of all the monitors till they match. Repeat weekly.
       (this is easier with a minolta color analyzer.)

Pierce
       
-- 
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