On 28.04.10 20:10, clipka wrote:
> Am 28.04.2010 19:00, schrieb Thorsten Froehlich:
>> On 27.04.10 23:05, clipka wrote:
>>> BTW, as a matter of fact, the wrong channel ordering is a 3.7 issue;
>>> POV-Ray 3.6 at least did it the right way round.
>>>
>>> I consider the use of RGB instead of YCbCr a bug (already filed as
>>> FS#103 ;-)).
>>
>> No, it isn't a bug. This *really* is intentional behavior! With the
>> correct settings in other places (not sure if they are), you can get rid
>> of a lot of color bleeding when using sharply ray-traced objects by
>> using RGB.
>
>  From experiments, I really don't see any advantage of RGB over YCbCr
> without chroma sub-sampling.

The way to measure is using statistical tests designed for image comparison 
... I still have the code somewhere.

> To the contrary: At the same output file size, YCbCr without chroma
> sub-sampling appears to give slightly superior quality.

Indeed, the file size of the RGB image will be larger because quantization 
works differently. In essence RGB works like three grayscale images in JPEG.

	Thorsten

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