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Filmscanners mailing list archive (filmscanners@halftone.co.uk)

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RE: filmscanners: Setting screen gamma problem



I did nto read the post thoroughly; but I would suggest that some of the
difference may very well be that your monitor is set at a different color
tempurature than those that you looked at which would effect the rendering
of the gamma setting.  Moreover, you may not have hour monitor's brightness
and contrast settings set at the same levels as was the case on the other
monitors.  Gamma settings is only one component in monitor calibration;
monitor calibration is not the same thing as color management but merely the
first step in color management.  For WYSIWYG to work across multiple
systems, all the systems have to be calibrated to the same standard of color
temperature, gamma, white point and black point, brightness and contrast.

Not to be funny; but how sure are you fo the acccurracy of your step wedge?
Most commercial step wedges are created using precision measurement
instruments and printed to precisely measurable standards.  Is it possible
that you personnally created step wedge may be out of gamut at the dark end
with respect to your monitor?  Is it possible that your web sit files might
be tagged with profiles that have small or inapproriate working color spaces
so that those receiving the image get images that their systems correct to
the embedded profile?

-----Original Message-----
From: owner-filmscanners@halftone.co.uk
[mailto:owner-filmscanners@halftone.co.uk]On Behalf Of Julian Robinson
Sent: Wednesday, June 27, 2001 7:50 AM
To: filmscanners@halftone.co.uk
Subject: filmscanners: Setting screen gamma problem


I know this topic is revisited ad nauseum, but I have just discovered that
what I thought was the Right Thing To Do does not appear to be right at
all.  On my system,  Adobe Gamma setup seems to be worse than no setup at
all.   I have cross posted this to Epson7x7, filmscanners, scan and digital
silver lists.

This post has become very long, read it if you are interested, but the
essence of my question is ...
******************************************************************
Please look at my simple greyscale step wedge at
www.austarmetro.com.au/~julian/stepwedge.htm and tell me if setting this up
for equal visual steps is a valid way of setting screen gamma, and does
*your* monitor show this wedge accurately?
******************************************************************

My problem was to make my recently web-published photos look reasonable on
other people's monitors.  I use PS5.5 and a Sony 400PS monitor.

I thought I had this all sussed, because I had religiously used Adobe Gamma
to give me what I assumed would be, maybe not perfect, but at least
ball-park OK settings.  I then looked at my pubescent website on someone
else's computer to discover all my deep beautiful saturated colors were
pale, insignificant and plain ugly.  I checked a couple of other computers
and while they vary, generally they give the same result.

My conclusion therefore was that for some reason my screen gamma is set to
make my screen look too dark.  So I checked Adobe Gamma again but it gave
me the same settings.

I can't afford a proper calibrator at this time, but decided to go back to
basics on the assumption that a step wedge greyscale from 0,0,0 to
255,255,255 should look balanced on my screen and the steps should all be
visible and roughly the same "brightness difference" between adjacent steps
across the scale.  I constructed a simple step wedge of 17 steps (0,0,0;
16,16,16; 32,32,32 ...255,255,255) and it looked bad.  The bottom 3  steps
were all black, which seemed to confirm that my monitor was NOT adjusted
correctly.

So I tried then to adjust gamma so that my stepwedge looked ok.  The
problem is that to achieve this, the gamma has to be set so high as to be
almost off the scale.  This is the same whether I use the slider on Adobe
Gamma Utility, or a different setting available in my Matrox card
adjustment software.   In both cases the gamma required to make the step
wedge look OK is way up the top end of the adjustment.  And of course all
my wallpapers and in fact all my images now look pale and washed out.

I have since looked at other photo sites to see how they look with my "new"
settings, and the situation is still confused.  On some sites their images
now look washed out, others look OK.  The average would be roughly half way
between my Adobe Gamma setting and my Step Wedge setting.

I am now completely confused, but aware that most of us are probably making
false assumptions about how other peoples' web photos are meant to
look.  For example, Lawrence Smith has a critique site whose address was
posted on a list today -  at http://www.lwsphoto.com/06_25_critique.htm. I
looked at this rather beautiful photo but didn't like how dark the stem and
leaves were, which agreed with a few of the comments posted at the
site.  But now that I have adjusted to my "Step Wedge gamma" and looked
again, the photo looks completely different, and the stem and leaves are
fine.  Which is right?  There is a HUGE difference.

Any answers to my questions welcomed...

-  is my assumption correct that such a stepwedge is a
    reasonable way to set up screen gamma?
- why doesn't the setting that this implies agree with the setting
suggested by
    Adobe Gamma? There is a HUGE difference.
- why is the correct gamma setting according to my stepwedge so high,
nearly off scale?
- what kind of gamma are most monitors actually aligned to IN PRACTICE?  I
know about nominal 1.8 and 2.2 for Apple and PCs, but it doesn't seem that
this bears much relationship to reality?

Julian

Julian Robinson
in usually sunny, smog free Canberra, Australia




 




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