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From: Quietman
Subject: Beta 37 changes to file gamma?
Date: 27 Apr 2010 21:39:20
Message: <4bd75988@news.povray.org>
Hi,

Just trying out beta 37 of povray and all output files are over bright 
compared with earlier versions.

I always add the following lines to the end of my povray.ini file.

; .png Image Type by default
Output_File_Type=N

; Picture brightness
Display_Gamma=1
File_Gamma=1

The display seems ok but the output file is lighter, even with the default 
file type (BMP).

Anyone else having trouble or is it my setup thats gone wrong somewhere?

Cheers.


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From: clipka
Subject: Re: Beta 37 changes to file gamma?
Date: 27 Apr 2010 21:56:57
Message: <4bd75da9$1@news.povray.org>
Am 27.04.2010 23:39, schrieb Quietman:

> Just trying out beta 37 of povray and all output files are over bright
> compared with earlier versions.

At present I can't rule out that I might have broken something with 
change #4932.

I'll try to recreate your scenario to see what's happening. Are using 
assumed_gamma? If so, what value it is set to?


BTW, regardless of whether this is a bug or not, be advised that 
File_Gamma=1 is not a good idea if you intend to share generated image 
files; and are you sure that your display subsystem does indeed have an 
overall gamma of 1.0 as indicated by Display_Gamma?


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From: clipka
Subject: Re: Beta 37 changes to file gamma?
Date: 28 Apr 2010 14:59:10
Message: <4bd84d3e$1@news.povray.org>
Am 27.04.2010 23:56, schrieb clipka:
> Am 27.04.2010 23:39, schrieb Quietman:
>
>> Just trying out beta 37 of povray and all output files are over bright
>> compared with earlier versions.
>
> At present I can't rule out that I might have broken something with
> change #4932.

Darn - I did indeed break it quite thoroughly.


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From: clipka
Subject: Re: Beta 37 changes to file gamma?
Date: 28 Apr 2010 16:01:01
Message: <4bd85bbd$1@news.povray.org>
Am 27.04.2010 23:39, schrieb Quietman:

> Just trying out beta 37 of povray and all output files are over bright
> compared with earlier versions.
>
> I always add the following lines to the end of my povray.ini file.
>
> ; .png Image Type by default
> Output_File_Type=N
>
> ; Picture brightness
> Display_Gamma=1
> File_Gamma=1

As a workaround, try setting File_Gamma to something like 0.98 or 1.02. 
(Any value smaller than 0.99 or greater than 1.01 should do.)


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From: Thomas de Groot
Subject: Re: Beta 37 changes to file gamma?
Date: 29 Apr 2010 08:21:13
Message: <4bd94179$1@news.povray.org>
"clipka" <ano### [at] anonymousorg> schreef in bericht 
news:4bd84d3e$1@news.povray.org...
>>
>> At present I can't rule out that I might have broken something with
>> change #4932.
>
> Darn - I did indeed break it quite thoroughly.

OK. So this means that, if we do not want to work around this now, we should 
better wait for the next beta (and stick with beta 36)?

Thomas


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From: clipka
Subject: Re: Beta 37 changes to file gamma?
Date: 29 Apr 2010 08:34:42
Message: <4bd944a2$1@news.povray.org>
Am 29.04.2010 10:21, schrieb Thomas de Groot:
> "clipka"<ano### [at] anonymousorg>  schreef in bericht
> news:4bd84d3e$1@news.povray.org...
>>>
>>> At present I can't rule out that I might have broken something with
>>> change #4932.
>>
>> Darn - I did indeed break it quite thoroughly.
>
> OK. So this means that, if we do not want to work around this now, we should
> better wait for the next beta (and stick with beta 36)?

I didn't break it as thoroughly as it seemed at first: The error only 
kicks in when File_Gamma is set to 1.0 (or, more precisely, 0.99 to 
1.01), which is normally not recommended anyway, so I fancy that the 
average user will not be affected. Phew. <wipes sweat off forehead>

So please do upgrade to beta 37 and give it a go, as there are many 
changes in there waiting for thorough testing.


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From: Thomas de Groot
Subject: Re: Beta 37 changes to file gamma?
Date: 29 Apr 2010 08:56:19
Message: <4bd949b3@news.povray.org>
"clipka" <ano### [at] anonymousorg> schreef in bericht 
news:4bd944a2$1@news.povray.org...
>
> I didn't break it as thoroughly as it seemed at first: The error only 
> kicks in when File_Gamma is set to 1.0 (or, more precisely, 0.99 to 1.01), 
> which is normally not recommended anyway, so I fancy that the average user 
> will not be affected. Phew. <wipes sweat off forehead>
>
> So please do upgrade to beta 37 and give it a go, as there are many 
> changes in there waiting for thorough testing.

OK. Anyway, the choice was taken out of hands as beta 36 crashes when going 
automatically to the update site. I produced a mini-dump file, should I send 
it somewhere? Have others the same experience?

Thomas


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From: Quietman
Subject: Re: Beta 37 changes to file gamma?
Date: 29 Apr 2010 15:42:12
Message: <4bd9a8d4$1@news.povray.org>
>clipka" <ano### [at] anonymousorg> wrote in message 
>news:4bd85bbd$1@news.povray.org...
> Am 27.04.2010 23:39, schrieb Quietman:
>
>> Just trying out beta 37 of povray and all output files are over bright
>> compared with earlier versions.
>>
>> I always add the following lines to the end of my povray.ini file.
>>
>> ; .png Image Type by default
>> Output_File_Type=N
>>
>> ; Picture brightness
>> Display_Gamma=1
>> File_Gamma=1
>
> As a workaround, try setting File_Gamma to something like 0.98 or 1.02. 
> (Any value smaller than 0.99 or greater than 1.01 should do.)

Setting them both to 1.02 fixed it.

Gamma settings have always been a source of trouble for my own renders with
povray. I can remember using version 3.5 and having to change gamma to
something lower. I stopped using assumed_gamma 1 in every file and changed
to the povray.ini settings when they were introduced.

I find using the defaults (2.2?) produces very bright washed out files. The
best fix I have found so far is to set both gamma settings to 1. It makes
the renders look natural in tone and colour for me.

I only do this for a hobby on a Samsung R700 laptop so sharing files with
anyone else isn't likely to happen. I assume it has a regular LCD screen (as
far as gamma goes).

Thanks for the help :)


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From: Warp
Subject: Re: Beta 37 changes to file gamma?
Date: 29 Apr 2010 16:24:49
Message: <4bd9b2d1@news.povray.org>
Quietman <quietman1968 at hotmail dot com> wrote:
> I find using the defaults (2.2?) produces very bright washed out files. The
> best fix I have found so far is to set both gamma settings to 1. It makes
> the renders look natural in tone and colour for me.

  If you had been using true gamma 2.2 for all your povray images for your
entire life, you would find a gamma of 1.0 unbearably dark.

  The reason is that if you were accustomed to the proper gamma, you would
be using the adecuate colors for that gamma (eg. 0.5 for a *truly* mid-gray
color, etc).

  As for image map images which don't have gamma info in them, they have to
be pre-gamma corrected manually when using the correct gamma for your system.
POV-Ray 3.7 implements now a keyword to do that.

  Question: If someone "lies" to POV-Ray by claiming that his system uses
a gamma of 1.0 when in reality it uses a gamma of 2.2, and renders an image
with that setting, will that image look the same in a different system with
a different gamma (eg. one with a gamma of 1.8), or will it look different?
If so, how different (brighter, darker...)?

-- 
                                                          - Warp


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From: clipka
Subject: Re: Beta 37 changes to file gamma?
Date: 29 Apr 2010 19:30:22
Message: <4bd9de4e@news.povray.org>
Am 29.04.2010 17:42, schrieb Quietman:

> I find using the defaults (2.2?) produces very bright washed out files. The
> best fix I have found so far is to set both gamma settings to 1. It makes
> the renders look natural in tone and colour for me.

I take a bold guess that this is probably because you're used to the way 
older POV-Ray versions did it, and have developed an instinct how to 
achieve the desired results for the old versions. Unfortunately that 
instinct don't work with the /more realistic/ model used in 3.7.

You may also have been fooled by earlier betas which couldn't handle 
input images properly (they did indeed get those input images too bright 
and washed-out).

Well, I guess I'm trying to evangelize you here, but in the end it's 
your choice of course.


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