In article <web.437641f51f234627b3cb5aca0@news.povray.org>, 
kdw### [at] earthlinknet says...
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> Patrick Elliott <sha### [at] hotmailcom> wrote:
> 
> > >What people are
> > screwing up is that they are setting the gamma to something that has
> > *nothing* to do with their displays actual gamma, so when they load it
> > one something else, it looks wrong. In the case of programs that
> > correctly handle the setting in the file, *they* are assuming the 'real'
> > gamma is different that your monitor and are dropping or increasing the
> > image colors to 'match' what they 'think' your display uses, which is by
> > default 1.0, not 2.2.
> > --
> 
> I have to admit that I didn't know monitors (all of them?) have a default
> gamma of 1. This raises a basic question. What is meant by a "gamma of 1.8"
> for the Mac and a "gamma of 2.2" for the PC? These are values that I've
> always taken as gospel.
> 
> Ken
> 
Ok. The difference is, load in something like Myst 2, then compare what 
'you' see, to what is on the box. For me, since the art was produced on a 
MAC, with a gamma of 1.8, but my monitor had a gamma of 1.0, the result 
was that the screen image was way to dark to see the details that the 
copy on the box had. To fix it I needed to increase the brightness in the 
display itself by 25-30%, and it still didn't look right. Gamma as used 
by video cards allows you to tell the card to increase the 'actual' 
signal strength for all colors, so the result is brighter on the display 
as well. To match the original MAC, with they display I have (before it 
got damaged by something and now works even worse), I would have had to 
adjust 'both' the brightness in the display's internal *and* the gamma on 
the card for that game.

Fact is, most are now trying to make them more or less the same for 'all' 
systems, but some difference still happens, so unless you adjust either 
the display or the card gamma, or possibly 'both', it will never look the 
same on your's as it does on someone else's, unless you happen to have 
the same drivers, card *and* display, and they have made no changes to 
these things. Photoshop and others, if they are smart (sort of), take the 
display gamma from the card, if they don't, then they assume a default 
value. In either case, they cheat, and actually 'bleach' the image, but 
increasing the apparent colors they display, instead of letting the 
hardware do it. Though some newer ones maybe have some way they ask the 
card to do so. Either way, they have no way to know how bright your 
display is, may not know if the card is already correcting gamma and 
simply assume, based on incorrect information, that they need to make an 
adjustment, because they think your gamma is not the same as what the 
image itself was created on, which could, defending one all the factors I 
mentioned, be anything from 1.0 to 2.2. If you don't know that your 
display is 2.2, or 1.8, or whatever, then don't tell POV-Ray to tell 
other things that it is. If you do know, then don't expect incorrectly 
configured systems to display it correctly, because most of them don't 
know what they 'own' gamma is, so can't correct it properly.

If you where doing high end photo editing, you would know what your gamma 
was, know how to get the programs set to know what gamma that is and 
'always' use gamma correction to make sure it comes out right. In theory 
using it in POV-Ray is good too, but most of us have no clue how to make 
sure all these things are set correctly for our own systems, so we get 
the equivalent of overexposed film instead, as a result of using a 
setting that isn't even the right one for our own hardware, then 
compounding the problem by using a program that doesn't know how to 
correctly adjust the image to that hardware.

Think of it this way. Someone tells you to label a box with a 
transparency in it with, "Use a 220 watt bulb to display.", you are using 
a 150 watt, but never bothered to check, and half the other people have 
100 watt, 120 watt, etc. What do you think the result of someone, even 
yourself, removing the dimmer 150 watt bulb, and installing a really 
bright 220 watt instead would be when looking at the transparency? *If* 
they projection was far enough away, it would look fine (the equivalent 
of having gamma 2.2 and the system 'knowing' its 2.2), but if your 
projecting at a distance appropriate for 150 watts.... (Anyone confused, 
replace the watts with something like a penlight, a full sized flashlight 
and a table lamp. Same sort of problem.)

-- 
void main () {

    call functional_code()
  else
    call crash_windows();
}

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