Christoph Hormann nous apporta ses lumieres ainsi en ce 05/08/2004 
09:44... :

> Alain wrote:
>
>>>
>> If outputing to PNG or PPM, you can set the bit-per-chanel to 
>> anything from 5 to 16 (default is 8). If you use, say, 10 bits and 
>> divide all your lights by 4 (or divide the diffuse and ambient values 
>> by 4), you can simulate a higher dinamic range. If doing this, be 
>> sure to lower the asc_bailout acordingly.
>
>
> No, high dynamic range is not the same as more than 8 bits per value. 
> It means the format can represent several orders of magnitude in color 
> values.  With 16 bit you can represent a contrast ratio of 65535:1 
> (meaning the smallest color difference that can be represented is 
> 1/65535 of the brightest color value in the image), a high dynamic 
> range format usually handles at least a few million. You could store 
> logarithmic values in an integer file format but simply scaling them 
> will not help.
>
> Christoph
>
I said "simulate a higher" dynamic range, like "faking it". I should 
have said "expanded dynamic range". In some cases, it can be enough, it 
depend on the particular case. I never wanted to imply "true" high 
dynamic range.

Alain

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