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Fredrik Eriksson wrote:
> 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.
>
24 bit per pixel should be enought to see no banding.
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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.
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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