If using a display with a gamma larger than 1.0 and running with an assumed
gamma of 1.0 as recommended, you will need to adjust the gamma of the image
being used as an image_map to have a gamma of 1.0 prior to use (*).

In other words the image_map image prior to use should look darker on a
display with a gamma of > 1.0 when you view it with for example photoshop
or similar tool.

There is also a display gamma setting, but unless you have changed it
yourself the default is set up as 2.2 and that is good for most display
systems.

(*) If your image looks 'right' on a display with a gamma of for example
2.2, it is not itself a linear image. Linear image = image with a gamma of
1.0.

Bill

Kyle <hob### [at] gatenet> wrote:

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Bill,

I was hoping to find a way to do this in the scene file to avoid
having to edit the image(s), but it may not be possible.  

Your suggestion does work very well, though.  I opened the image in
Gimp and adjusted the gamma by 0.45 (the inverse of 2.2).  The
rendered colors look very nice now.  

Thanks for your suggestion.


Kyle

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Kyle <hob### [at] gatenet> wrote:
> Bill,
>
> I was hoping to find a way to do this in the scene file to avoid
> having to edit the image(s), but it may not be possible.

Jaime Vives Piqueres Lightsys package lets you easily adjust the brightness,
contrast and gamma adjustment of any pigment, including image_maps.
Lightsys comes with easy-to-follow demos of the image processing
capabilities. You could probably still utilize these macros, even if you
don't want to use the full power of Lightsys.

> Your suggestion does work very well, though.  I opened the image in
> Gimp and adjusted the gamma by 0.45 (the inverse of 2.2).  The
> rendered colors look very nice now.

Post a reply to this message

news:vp9bd1p330mntk3k9dhlfch4csv2215j12@4ax.com...
> Hi all.
>
> I hope this hasn't been asked before, or is answered somewhere in the
> manual that I have overlooked, but here goes...
>
> I am using an image_map as a pigment for an object.  Once rendered,
> the color of the object looks quite faded, compared to the image that
> is used for the image_map.  I found that adjusting the assumed_gamma
> in global_settings from 1 to 2.2 enhances the color of the object.  Is
> there a method to enhance the image_map pigment without affecting the
> entire image?
>
>
> Thanks,
>
> Kyle
>

When I use an image_map as a pigment, I always set finish{diffuse  1}

Marc

Post a reply to this message

On Fri, 15 Jul 2005 06:40:25 EDT, "PM 2Ring" <nomail@nomail> wrote:

>Jaime Vives Piqueres Lightsys package lets you easily adjust the brightness,
>contrast and gamma adjustment of any pigment, including image_maps.
>Lightsys comes with easy-to-follow demos of the image processing
>capabilities. You could probably still utilize these macros, even if you
>don't want to use the full power of Lightsys.


I downloaded Lightsys some time ago, but haven't had a chance to check
it out.  I've noticed quite a few scenes that use it.  I guess its
time to go learn something new...

Thanks!


Kyle

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On Fri, 15 Jul 2005 20:28:55 +0200, "Marc Jacquier"
<jac### [at] wanadoofr> wrote:

>When I use an image_map as a pigment, I always set finish{diffuse  1}
>

No help in this case.  It's too washed out, similar to increasing the
light intensity.  Thanks for the suggestion, though.


Kyle

Post a reply to this message

Here are the results of a few tests...  

The problem:  When using a jpg image in an image mapped pigment, the
rendered colors are very washed out as compared to the original image.

After a reply from William Pokorny on this issue, I opened the
original image in Gimp, adjusted the gamma by 0.45, which is 1/2.2,
then saved it.  The colors of the rendered image were correct.

This got me to thinking about saving the original image in a format
that stores gamma data and if POVRay would account for this...  

I first saved the original image in png format without gamma.  The
colors of the rendered image were washed out, just like with the
original jpg image.  

I then saved the original image in png format with gamma.  The colors
of the rendered image are correct!

Apparently, POVRay does adjust for the gamma value that is saved with
an image if it is used in an image mapped pigment.

I hope this info helps someone else out...


Kyle



On Wed, 13 Jul 2005 19:59:55 -0400, Kyle <hob### [at] gatenet> wrote:

>Hi all.
>
>I hope this hasn't been asked before, or is answered somewhere in the
>manual that I have overlooked, but here goes...
>
>I am using an image_map as a pigment for an object.  Once rendered,
>the color of the object looks quite faded, compared to the image that
>is used for the image_map.  I found that adjusting the assumed_gamma
>in global_settings from 1 to 2.2 enhances the color of the object.  Is
>there a method to enhance the image_map pigment without affecting the
>entire image?
>
>
>Thanks,
>
>Kyle

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I may be talking to myself here, but...

If anyone's interested, I am going to post a scene file containing a
macro in p.b.s-f that allows you to adjust an image mapped pigment, or
any pigment for that matter, by a specified gamma value.  Look for a
post with the same subject.  I hope this is useful to someone.


Kyle

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Whoops, accidentally posted in p.t.s-f


Kyle

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Kyle <hob### [at] gatenet> wrote:

> I then saved the original image in png format with gamma.  The colors
> of the rendered image are correct!
>
> Apparently, POVRay does adjust for the gamma value that is saved with
> an image if it is used in an image mapped pigment.
>
> I hope this info helps someone else out...
>
>
> Kyle
>

Hi!  Thanks for posting this; I've been trying to figure out a solution to
the exact same problem, and your suggestion has solved it!

Ken

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