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[filmscanners] RE: Density vs Dynamic range>AUSTIN (2a)



That's correct.
CCD's output is actually pixel's energy which is expressed in their analog
charge (you can imagine them as a capacitor-like cells). Further, their
energy, expressed in volts
(or milivolts in reality), is translated into digital domain by some kind of
A/D through some additional processing (gain and digital filtration).

Regards,
Alex Z

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Isidoro Orabona
Sent: Monday, June 17, 2002 5:48 PM
To: alexz@zoran.co.il
Subject: [filmscanners] Re: Density vs Dynamic range>AUSTIN (2a)


Hi Austin,

your message that I refer to is at the bottom of my e-mail, this is:

>Sorry to sound "snide", but er, DUH!  Do you know of a CCD that outputs
>AC???  I don't!!!  It's ALL D/C measurements as it relates to scanners (and
>actually, even audio).

The statement in capitals is instead mine.

I claim that all useful signals are AC, or that can be modeled as AC
signals. The DC measurement isn't the signal itself, but only a measure,
just so, of part of its nature in a given instant. Then I claim that the CCD
outputs a analog AC signal, later converted via A/D converters.
At last, I want underline that no one can talk about signal and noise if he
don't state what the signal is and what the "noise" that MAY obscure it.
Only after you "modeled" your system, you can apply the formulas (and yours
are correct). When you read the specs of a A/D converter, for example, you
read signal to noise ratio in given (standard == agreement) conditions and
with a given (standard) test set, that together establish "the system".

Regards,

Isidoro

>From: "Austin Franklin" <darkroom@ix.netcom.com>
>Reply-To: filmscanners@halftone.co.uk
>To: isiora02@hotmail.com
>Subject: [filmscanners] RE: Density vs Dynamic range>AUSTIN (2a)
>Date: Mon, 17 Jun 2002 09:53:11 -0400
>
>
> > Hi,
> >
> > I am not interested in the question too much, but when I have
> > read the last
> > message by Austin...
> >
> > ALL USEFUL SIGNALS (= INFORMATION) ARE AC SIGNALS, "CONSTANT
> > SIGNAL" IS ONLY
> > AN OFFSET.
>
>Hi Isidoro,
>
>I don't believe I said the above...
>
>Regards,
>
>Austin
>
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