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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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