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Re: [OM] (IMG) Deep Purple

Subject: Re: [OM] (IMG) Deep Purple
From: "Carlos J. Santisteban" <zuiko21@xxxxxxxxx>
Date: Fri, 12 Jun 2009 18:29:36 +0200
Hi Fernando and all,


> From: Fernando Gonzalez Gentile <fgnzalez@xxxxxxxxxxxxx>
> Your sentence: " ... a film negative or slide has substantial random
> noise (grain) which will create the effect of greater bit-depth than is
> actually there." is almost the theory I was looking for.
>

This is called dithering, and it's used almost everywhere in computers --
printers etc. However, if you expect to do severe curves/gamma corrections,
you need the extra bit-depth, otherwise you'll get a nasty posterization.

BTW, the opposite of dithering is called anti-aliasing -- with some extra
bit depth it may compensate for the lack of resolution.


> Same runs for your sentence: " ...in Nikonscan, there is the scanning
> bitdepth and then there is the file-save bitdepth."


Scanning software is something a bit obscure to me... obviously, one thing
is the scanning bitdepth, which is the precision to digitize the CCD's
signal; and another is the file-save bitdepth, which is what PS or whaterver
program will receipt. Again, if you do some tweaking at the scanner
settings, keep scanning bidepth as high as possible, you may even save at a
lower bitdepth and shrink the files.

- measuring information in bytes, defines what random noise is. Am I too
> deterministic in my philosophic cornerstones, that I don't believe in
> random facts other than in maths.


A byte is just a number between 0 and 255 -- or -128 to 127, if you prefer.
Random noise is generated in the analog world: stray electrons "bouncing" on
the CCD, hole recombination on its (analog) electronic amplifiers or, with
quite a different pattern, the grain of the scanned film. Once digitized,
the obtained bytes will show some deviation from the "correct" values.

Probably there's no real random in nature... but we're living in such a
complex pseudo-random generator that gives the opposite impression ;-)

My daughter is calling me, must go out now.
>

You must obey at once, then :-)

Cheers,
-- 
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
-- 
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