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In article <40329903@news.povray.org>,
"Gilles Tran" <gitran_nospam_@wanadoo.fr> wrote:
> To be honest, after reading the docs over and over and reading many
> discussions in these groups, I'm still unable to understand what are the
> "right" gamma settings for a given computer, and the fact that the gamma
> test doesn't seem to work on flat screens adds to my confusion :(
assumed_gamma should be 1 for new scenes. Display_Gamma should be the
gamma of the display your image will be viewed on. LCD displays have an
S-shaped response curve, the power curve used to approximate the
response of CRT displays doesn't work well at all on them, but I think
the system usually maps it to either a CRT response curve or a linear
(gamma 1) function. I don't have any technical references for this, it
just seems to match the behavior I've seen.
The gamma actually used to correct things is Display_Gamma/assumed_gamma.
If assumed_gamma is 1, that is just Display_Gamma, otherwise it corrects
the colors for a scene designed on a machine with a display gamma of
assumed_gamma, but without any gamma correction. Maybe this will make it
clearer:
Say you make a scene on a machine with gamma of G1. When you do this,
the version of POV you use doesn't support gamma correction, so you just
choose the colors to look right, essentially encoding the gamma into the
scene itself.
Years later, you dig up the scene in some archives and render it. It was
designed for a display with a different gamma, and doesn't turn out
right, so you add an assumed_gamma statement with the gamma of your old
machine. The scene now renders correctly.
New scenes should just use assumed_gamma 1, to use the display gamma of
the machine the scene is being rendered on.
--
Christopher James Huff <cja### [at] earthlink net>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/
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"Christopher James Huff" <cja### [at] earthlinknet> wrote in message
news:cjameshuff-29D3EA.18365917022004@news.povray.org...
> In article <403256d8$1@news.povray.org>,
> "Norbert Kern" <nor### [at] t-onlinede> wrote:
>
> > why you use "assumed_gamma = 1;" when you actually use a value of 2.2 or so?
> > This was also true for each of your excellent example images for your
> > Maklecloud macro.
>
> Hmm? You're supposed to use assumed_gamma 1 for new scenes...it only
> exists to provide a way to correctly render scenes designed without
> gamma correction.
Then why isn't 1 the default?
maybe a stupid question, I don't really fully understand that gamma-stuff :-/
cu!
--
camera{location-z*3}#macro G(b,e)b+(e-b)*(C/50)#end#macro L(b,e,k,l)#local C=0
;#while(C<50)sphere{G(b,e),.1pigment{rgb G(k,l)}finish{ambient 1}}#local C=C+1
;#end#end L(y-x,y,x,x+y)L(y,-x-y,x+y,y)L(-x-y,-y,y,y+z)L(-y,y,y+z,x+y)L(0,x+y,
<.5,1,.5>,x)L(0,x-y,<.5,1,.5>,x) // ZK http://www.povplace.be.tf
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in news:4032de94$1@news.povray.org Zeger Knaepen wrote:
> Then why isn't 1 the default?
> maybe a stupid question, I don't really fully understand that
> gamma-stuff :-/
>
The default is to render to an image with gamma=1 (no gamma correction),
this means that in the resulting file the value for a 33.333% gray is at
one-third of the maximum value (white).
If you put in assumeg_gamma = 1 it will render to a gamma as set by the
Display-Gamma value. The before mentioned 33.333% gray wil now not have a
value at one-third of the maximum. Yet on your monitor you will see it as
33.333% grey.
Ingo
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in news:Xns94935ECD1E30Fseed7@news.povray.org ingo wrote:
> The before mentioned 33.333% gray wil now not have a
> value at one-third of the maximum.
Should have added that you can easy check this by rendering images of a 5-
step grayscale. Open the images in a hex-editor and you can see the values
written to the file. ppm format is probably what you should choose for
output.
Ingo
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In article <4032de94$1@news.povray.org>,
"Zeger Knaepen" <zeg### [at] studentkuleuvenacbe> wrote:
> Then why isn't 1 the default?
So you can render scenes without any gamma correction. No assumed_gamma,
no gamma correction.
--
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/
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"Christopher James Huff" <cja### [at] earthlinknet> wrote in message
news:cjameshuff-5F0F04.07454618022004@news.povray.org...
> In article <4032de94$1@news.povray.org>,
> "Zeger Knaepen" <zeg### [at] studentkuleuvenacbe> wrote:
>
> > Then why isn't 1 the default?
>
> So you can render scenes without any gamma correction. No assumed_gamma,
> no gamma correction.
ah, excellent :)
I was wondering about that :)
tnx!
cu
--
camera{location-z*3}#macro G(b,e)b+(e-b)*(C/50)#end#macro L(b,e,k,l)#local C=0
;#while(C<50)sphere{G(b,e),.1pigment{rgb G(k,l)}finish{ambient 1}}#local C=C+1
;#end#end L(y-x,y,x,x+y)L(y,-x-y,x+y,y)L(-x-y,-y,y,y+z)L(-y,y,y+z,x+y)L(0,x+y,
<.5,1,.5>,x)L(0,x-y,<.5,1,.5>,x) // ZK http://www.povplace.be.tf
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> > > I'm thinkin' 5th Element.
> >
> > I was about to say the same. I found myself looking for Leeloo there.
:-)
> >
> > Jaw-dropping beautiful. But that's Gilles Tran's, so that's kinda
> expected.
> > :-)
>
> Wow, Gilles landed Leelo? Gilles; make sure you don't kiss her without her
> permission. :-)
Hehehe... Big badabum! I love that movie. :-)
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From: Greg M Johnson
Subject: Re: Sci-fi objects demo image (190 kb)
Date: 18 Feb 2004 22:45:05
Message: <40343141@news.povray.org>
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This is a great gift to humanity.
There is an irony however here in that you're suggesting your files are for
the IRTC.
If say I were to to an anim about MIME Man riding around in one of those
ships, I'd have to settle for an **TEN FRAME** animation. It takes 1.5
hours to render 320x240 on my 2.8GHz PC. Yes there are tricks to lower
resolution temporarily, but if one were to do an anim project of *this
quality*, there wouldn't be much opportunity to make many revisions (I was
so happy when I could do one a day) over the course of a 90-day period
unless of course one had your own render farm.
It's just an irony. The first and second place winners for the last round
(also in my individual voting) were both very cartoony, possibly really
quick renders.
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"Roberto A." <wol### [at] hot-mailcom> wrote in message
news:40337e0d$1@news.povray.org...
> > > > I'm thinkin' 5th Element.
> > >
> > > I was about to say the same. I found myself looking for Leeloo there.
> :-)
> > >
> > > Jaw-dropping beautiful. But that's Gilles Tran's, so that's kinda
> > expected.
> > > :-)
> >
> > Wow, Gilles landed Leelo? Gilles; make sure you don't kiss her without
her
> > permission. :-)
>
> Hehehe... Big badabum! I love that movie. :-)
It is sweet. My favorite line from the movie is when Zorg says into the
phone, "Are you making fun of me?" I loved the subtelty of that -- it
basically tells an entire back-story in one sentence.
Ecto gammut! :-)
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"Gilles Tran" <gitran_nospam_@wanadoo.fr> wrote in
news:40314abf@news.povray.org:
> I thought I might jump the gun and put
> them for download now if people want to use them for the IRTC, the IMP
> (I'd love to see those in an animation) or anything else.
>
>
Wow! Thanks. I will alert the IMP members ;)
--
Tom
_________________________________
The Internet Movie Project
http://www.imp.org/
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