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

["Anthony Atkielski" <anthony@atkielski.com>]

Usually systems that can handle high signal rates can also handle low rates,
often right down to DC.  In imaging, for example, a system that can handle
1200x1200-pixel images can also handle 10x10 pixel images, and a system that
can handle a pattern of pure black and white vertical lines can also handle
a featureless neutral gray.

----- Original Message -----
From: "Paul D. DeRocco" <pderocco@ix.netcom.com>
To: <anthony@atkielski.com>
Sent: Tuesday, June 18, 2002 02:21
Subject: [filmscanners] RE: Density vs Dynamic range>AUSTIN (2a)


The issue is whether or not you need frequency response down to DC. A
scanner obviously does, because a series of alternating black and gray lines
looks different from a series of alternating gray and white lines, even
though they have the same AC component.

--

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

> From: Anthony Atkielski
>
> But samples are not signals, and DC is not a signal.  A current or voltage
> that does not vary (i.e., DC) carries no information, and is thus not a
> signal.  All signals are AC.  More precisely, all signals vary
> over time; DC
> does not vary over time; therefore DC and signals are mutually exclusive.

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