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

["Paul D. DeRocco" <pderocco@ix.netcom.com>]

> From: Karasev, Alexander
>
> Actually most observers can, in smooth areas (sky, etc.) particularly in
> midrange tones.
>
> Create in Photoshop, Paintbrush, CorelDraw, or other software, two large
> adjacent rectangles or other figures, one with a solid RGB24 fill of
> [128,128,128] (i.e. neutral grey on the scale of 0-255), and
> another either
> [129,129,129] or [128,128,129]. Most people who used to argue for lack of
> benefit [if only in final output] of higher color depths than 8 bits /
> channel, are usually quite stunned at their ability to pick up the
> difference, often at a glance.
>
> That means, the same limitations can apply to photo reproductions of
> substantially high quality and low noise, of smooth areas (such as a
> clear blue or uniformly "grey" sky).

But the level of noise in a real-world image, either from film grain or CCD
noise, is always greater than a least-significant-bit of an 8-bit value.
This means that finer gradations are indeed represented in an 8-bit image
through dithering. Your test isn't a fair test.

--

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

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