From: d9hh@dtek.chalmers.se (Henrik Harmsen)
Subject: Re: 16 million vs 65 thousand colors
Nntp-Posting-Host: hacke11.dtek.chalmers.se
Organization: Chalmers University of Technology, Gothenburg Sweden
Lines: 37

andrey@cco.caltech.edu (Andre T. Yew) writes:

>d9hh@dtek.chalmers.se (Henrik Harmsen) writes:

>>1-4 bits per R/G/B gives horrible machbanding visible in almost any picture.

>>5 bits per R/G/B (32768, 65000 colors) gives visible machbanding

>>color-gradient picture has _almost_ no machbanding. This color-resolution is 

>>see some small machbanding on the smooth color-gradient picture, but all in all,
>>There _ARE_ situiations where you get visible mach-banding even in
>>a 24 bit card. If
>>you create a very smooth color gradient of dark-green-white-yellow
>>or something and turn
>>up the contrast on the monitor, you will probably see some mach-banding.

>    While I don't mean to damn Henrik's attempt to be helpful here,
>he's using a common misconception that should be corrected.

>    Mach banding will occur for any image.  It is not the color
>quantization you see when you don't have enough bits.  It is the
>human eye's response to transitions or edges between intensities.
>The result is that colors near the transistion look brighter on
>the brighter side and darker on the darker side.

>--Andre

Yeah, of course... The term 'mach banding' was not the correct one, it should've
been 'color quantization effect'. Although a bad color quantization effect could
result in some visible mach-bands on a picture that was smooth before it was
quantizised.

--
Henrik Harmsen     Internet:  d9hh@dtek.chalmers.se
               Chalmers University of Technology, Sweden. 
      "I haven't lost my mind -- it's backed up on tape somewhere."
