[filmscanners] RE: IV ED dynamic range... DYNAMIC RANGE!

["Kapetanakis, Constantine" <KAPETAC@polaroid.com>]

That is wrong.
The light scattering characteristics of different media are different. If i
am not mistaken that is called the "Q-factor".
Without elaborating much try this very simple experiment.
Take two different media of similar densities, as measured with a
densitometer i.e. a ccNeutral density filter and a gray scale target of
either film or another base material. Scan both with the same scanner while
disabling auto-exposure and you will get different results.



-----Original Message-----
From: Clark Guy [mailto:guy.clark@sbt.siemens.com]
Sent: Thursday, August 08, 2002 2:36 PM
To: KAPETAC@polaroid.com
Subject: [filmscanners] RE: IV ED dynamic range... DYNAMIC RANGE!


HI, Constantine!

I'm not sure I agree with that statement.... What is needed is a standard
way of measuring against some targets of known density.   That doesn't
require any "standard" image slide or anything.  All that is required is a
set of "filters" that have known densities.  After all, density is an
absolute thing (this filter has a density of 50%, or that filter has an
attenuation of 20dB, or something like that.)  It's not "rocket science!"!


To measure the dynamic range of the scanner would simply be to monitor the
output as one places filters of different density (or attenuation) between
the light source and the detector.  When the output either ceases to change
with increasing density, (or decreasing density) that is one limit of the
system. (One might be even more fussy and require that the output change be
linear over the claimed range!)   I think that this should be (and probably
is already) part of the design verification process for any such product.

I had to do much the same thing in determining the linear range of
photometric devices for the medical diagnostics (and pharmaceutical)
industries earlier in my engineering career.  If I could do it, I'm sure the
digital imaging industry can!   ;-)

Guy Clark

-----Original Message-----
From: Kapetanakis, Constantine [mailto:KAPETAC@polaroid.com]
Sent: Thursday, August 08, 2002 12:19 PM
To: Clark Guy
Subject: [filmscanners] RE: IV ED dynamic range... DYNAMIC RANGE!


What the ISO people don't have is the target. You need a film based target,
any other non film based target will give "garbage" data.

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