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Message: #78278, S/7  Aldus PhotoStyler
Date:    Tue, Nov 23, 1993 10:55:09 PM
Subject: Monitor Calibration GIF
From:    Richard Levy 73340,1140
To:      All (deletable)

I've just dl'd MONCAL.GIF and am now wondering how to deal with it.

It is a background/foreground monitor matching chart, all various grays, 
similar to the RGB chart in PS 2's monitor setup. Each grey square has a 
monitor gamma value printed in it and the square that most nearly disappears 
represents the current gamma value of your monitor. Very nice but what do I 
do with this information?

e.g. my situation. Using the PStyler chart I get values around 1.75 to 1.8 
for all three colors (that is if I enlarge the bars to about two thirds my 
screen height - when they are small the correct values are totally different 
but that's another question altogether). Now, when I display moncal.gif 
(copyright Thomas D. Price 1993), the box which just about disappears has a 
value of 2.1.

Fine, now what? If I return to monitor set up and change the RGB bar values 
to 2.1, they look wrong and, obviously so does grey box 2.1 when I return to 
it. In fact the correct grey box now appears to be around 1.8! Well it didn't 
take but a few hours or so to realize this was a loop from which there was no 
escape (I'm not stupid, afterall!).

Seriously, Thomas, I like your chart, but how do I use its information?

Richard
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Message: #78291, S/7  Aldus PhotoStyler
Date:    Wed, Nov 24, 1993 12:31:14 AM
Subject: #78278-Monitor Calibration GIF
From:    Tom Price 75300,620
To:      Richard Levy 73340,1140 (received) (deletable)

Richard,

The results you get with MONCAL.GIF indicate that your monitor's native
gamma is about 2.1. If you set the Monitor Gamma in the PS2 Preferences area
to 2.1 you are essentially applying the correction for your particular
monitor so that displayed images will appear as they should on the default
KCMS 1.8 monitor. My monitor's native gamma is 1.95 and when I set that in
the Preferences box, MONCAL.GIF's 1.8 box blends best with the background.
At least that's the way PS2 and KCMS appear to work.

Acutally, I didn't have PhotoStyler in mind when I designed MONCAL.GIF. The
idea was that in future image viewers we wanted to be able to display any
image correctly on any monitor. To do this, we need to know the image gamma
and the monitor gamma, so that we can adjust the incoming data on-the-fly.
MONCAL.GIF provides a way to measure the monitor's gamma. Now all that
remains is devising some standard ways to convey the image gamma value to
the image decoder/viewer. The hope is that future GIF and JPEG standards
will address this in the form of a marker field that can be read by the
viewing software.

               Tom

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Message: #78303, S/7  Aldus PhotoStyler
Date:    Wed, Nov 24, 1993 3:28:16 AM
Subject: #78278-Monitor Calibration GIF
From:    Bradford K Levy 72170,1503
To:      Richard Levy 73340,1140 (received) (deletable)

Richard - gamtut.txt (lib 0 or 14) will answer some of your question about 
the getting different gamma readings with different enlargements.

-brad
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Message: #78308, S/7  Aldus PhotoStyler
Date:    Wed, Nov 24, 1993 7:03:08 AM
Subject: #78278-Monitor Calibration GIF
From:    Bill Harris 70674,364
To:      Richard Levy 73340,1140 (received) (deletable)

Richard--

You're right, it *is* an endless loop <S>.

The Kodak Color Management System is affecting things... it assumes a monitor 
gamma of 1.8 and alters your view accordingly.  MONCAL.gif is used to 
determine your monitor's gamma value and should be looked at with a non-
PStyler 2.0 (non-CMS) viewer.  Your observed value of 1.8 +/- sounds 
reasonable.

There is a replacement image to PSGAMMA.TIF in the Library, PSGAM1.GIF.  It 
uses a different/better background pattern than PSGAMMA (you'll need to 
convert it to a TIFF before using it).

What monitor/video card/video mode are you using?

--Bill