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using pov-ray 3.6.1 for windows on windows XP...
Should I be seeing the banding produced in this minimal scene file?
(Is this a limitation of POV's precision, or a bug? banding is stronger in
original bmp of picture)
camera { location <-4,4,-4> look_at <0,0,0> right <1,0,0> up <0,1,0> }
light_source { <1,1,-1> color rgb 1 }
plane { <0,1,0>, 0 pigment{color rgb 1} }
and result....
Post a reply to this message
Attachments:
Download 'bands.jpg' (20 KB)
Preview of image 'bands.jpg'
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On Sun, 31 Jul 2005 17:26:22 +0200, Hall <tre### [at] ww-interlink net> wrote:
> using pov-ray 3.6.1 for windows on windows XP...
> Should I be seeing the banding produced in this minimal scene file?
> (Is this a limitation of POV's precision, or a bug? banding is stronger
> in original bmp of picture)
>
> camera { location <-4,4,-4> look_at <0,0,0> right <1,0,0> up <0,1,0> }
> light_source { <1,1,-1> color rgb 1 }
> plane { <0,1,0>, 0 pigment{color rgb 1} }
>
> and result....
The banding results from the limits in the precision of the output format
and the final display device. In a 24-bit colour image, there are only 256
shades of pure gray.
Possible remedies:
- Introduce more colour in the image.
- Output at a higher bit depth (e.g. 16bpp/48bpp png), and use image
manipulation software to dither the image down to 8 bits per colour
channel.
--
FE
Post a reply to this message
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Hall wrote:
> using pov-ray 3.6.1 for windows on windows XP...
> Should I be seeing the banding produced in this minimal scene file?
> (Is this a limitation of POV's precision, or a bug? banding is stronger in
> original bmp of picture)
>
> camera { location <-4,4,-4> look_at <0,0,0> right <1,0,0> up <0,1,0> }
> light_source { <1,1,-1> color rgb 1 }
> plane { <0,1,0>, 0 pigment{color rgb 1} }
>
> and result....
>
>
>
>
I don't see the banding.
See the manual 2.4 Questions and Tips
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Fredrik Eriksson wrote:
> On Sun, 31 Jul 2005 17:26:22 +0200, Hall <tre### [at] ww-interlinknet> wrote:
>
>> using pov-ray 3.6.1 for windows on windows XP...
>> Should I be seeing the banding produced in this minimal scene file?
>> (Is this a limitation of POV's precision, or a bug? banding is
>> stronger in original bmp of picture)
>>
>> camera { location <-4,4,-4> look_at <0,0,0> right <1,0,0> up <0,1,0> }
>> light_source { <1,1,-1> color rgb 1 }
>> plane { <0,1,0>, 0 pigment{color rgb 1} }
>>
>> and result....
>
>
>
> The banding results from the limits in the precision of the output
> format and the final display device. In a 24-bit colour image, there
> are only 256 shades of pure gray.
>
> Possible remedies:
> - Introduce more colour in the image.
> - Output at a higher bit depth (e.g. 16bpp/48bpp png), and use image
> manipulation software to dither the image down to 8 bits per colour
> channel.
>
24 bit per pixel should be enought to see no banding.
...
... removed text ...
...
I wouldn't believe it but I see the banding in my reder (3.6.1)
as well. A color analysis via gimp showed that the color
of neighbouring bands differ by just one value step (8 bit: 1 step
1/255). This means that a smooth gray gradient with closed one color
fields cannot be achieved with 24bit colours.
I wasn't aware of this.
No I understand why dithering is necessray for 24bpp images
with smooth (gray) gradients.
Interesting. This is followed by some thoughts about 16bpc
resolution...
Thanks for the hint.
Sebastian
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> I wouldn't believe it but I see the banding in my reder (3.6.1)
> as well. A color analysis via gimp showed that the color
> of neighbouring bands differ by just one value step (8 bit: 1 step
> 1/255). This means that a smooth gray gradient with closed one color
> fields cannot be achieved with 24bit colours.
More precisely, it can't be achieved with 24-bit RGB. There are colour
bases in which 24-bit precision is easily enough to get a smooth
gradient.
--
There may come a time The open palm of desire,
When I will lose you, ]http://surreal.istic.org/[ The rose of Jericho,
Lose you as I lose my sight, Soil as soft as Summer,
Days falling backward into velvet night; The strength to let you go.
Post a reply to this message
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> More precisely, it can't be achieved with 24-bit RGB. There are colour
> bases in which 24-bit precision is easily enough to get a smooth
> gradient.
Even more precisely, a smooth *grey* gradient. Sorry for the inaccuracy.
I noticed it as soon as I pressed send. :-(
--
There may come a time The open palm of desire,
When I will lose you, ]http://surreal.istic.org/[ The rose of Jericho,
Lose you as I lose my sight, Soil as soft as Summer,
Days falling backward into velvet night; The strength to let you go.
Post a reply to this message
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Hall nous apporta ses lumieres en ce 2005-07-31 11:26:
> using pov-ray 3.6.1 for windows on windows XP...
> Should I be seeing the banding produced in this minimal scene file?
> (Is this a limitation of POV's precision, or a bug? banding is stronger in
> original bmp of picture)
>
> camera { location <-4,4,-4> look_at <0,0,0> right <1,0,0> up <0,1,0> }
> light_source { <1,1,-1> color rgb 1 }
> plane { <0,1,0>, 0 pigment{color rgb 1} }
>
> and result....
>
>
>
>
I don't see any banding, display set at 32 (24) BBP.
Switching to 16 BBP and I dee very distinct and distracting banding. Back to 32 BBP!
Alain
Post a reply to this message
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Are you sure this isn't a what-his-name optical illusion? A mach band. The
one where the mind adds color banding. Have you taken the low bit image
into a manipulation program and run the eyedropper over it, to make sure
the bands are real?
-s
5TF!
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"Hall" <tre### [at] ww-interlinknet> wrote in message
news:42eceda8@news.povray.org...
> using pov-ray 3.6.1 for windows on windows XP...
> Should I be seeing the banding produced in this minimal scene file?
> (Is this a limitation of POV's precision, or a bug? banding is stronger in
> original bmp of picture)
>
> camera { location <-4,4,-4> look_at <0,0,0> right <1,0,0> up <0,1,0> }
> light_source { <1,1,-1> color rgb 1 }
> plane { <0,1,0>, 0 pigment{color rgb 1} }
>
> and result....
Are you running an ICC profile on your monitor?
If you are seeing *colour* bands (such as slightly red, green, or blue hues when
compared with neighbouring bands) in this greyscale image (even after you
desaturate it, or convert it to a pure greyscale image, in a paint program), it
could be because you're running an ICC profile for your monitor and, in the
process of changing the output signal to make it match a specific response
curve/black point/colour temperature, is introducing slight variations in the
output hue. Thus a specific output level like RGB 128, 128, 128, could become
129, 128, 128, causing one band to appear slightly red, while the one next to it
at RGB 127, 127, 127 could be changed to 127, 128, 127, making it appear
slightly blue. This can also introduce (if the profile isn't accurate) larger
than normal steps in the lightness of bands.
Check your colour management to see if a profile is enabled - if it is, try
disabling it, restarting, and checking if the bands are gone (or aren't as
significant).
Lance.
thezone - thezone.firewave.com.au
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"Lance Birch" <-> wrote in message news:42eda11f$1@news.povray.org...
<snip>
> at RGB 127, 127, 127 could be changed to 127, 128, 127, making it appear
> slightly blue.
Err... green. :)
Lance.
thezone - thezone.firewave.com.au
Post a reply to this message
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