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[filmscanners] RE: 8bits vs. 16bits/channel: can the eye seethe difference



> From: Austin Franklin
>
> I agree with that, but that's not really dithering.  That's merely a
> property of averaging, and how your eye works.  Dithering is deliberately
> adding random noise to a signal.  What you are describing is called
> aliasing.  They are entirely different.

No, it's dithering, not aliasing. Aliasing is the translation of frequencies
by sampling.

Whether the noise is deliberate or accidental is unimportant. The blue sky
has no appreciable noise, but the film grain or CCD adds some, resulting in
a signal that can be truncated to eight bits and yet still retain more than
eight bits of useful information at lower spatial frequencies.

> I don't believe that is true.  That is only used in the lower and some
> intermediate level CD players.  It's called delta-sigma conversion, and I
> was one of the original developers of this technique.  The high
> end units I
> am aware of still use very high end 20 bit A/D converters.  But,
> that's not
> got anything to do with dithering either ;-)  See my other post for a
> Digital Signal Processing definition of "dither".

I don't know what to make of this. You claim to be one of the original
developers of delta-sigma conversion, yet you then say it has nothing to do
with dithering? When you do 1-bit delta-sigma A/D conversion, the resulting
bit stream equals the signal plus high-frequency noise. When low-passed, the
noise is reduced, and the original signal is reconstructed.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@ix.netcom.com

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