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

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

You may use other filters but must be able to correlate to a "film density".
This correlation is not linear and will be different for each scanner.
The problem arises from the fact that a densitotemeter reads densities
differently than a scanner. A densitometer captures all light passing
through the media under test, while a scanner captures light entering
through its lens aperture.

-----Original Message-----
From: Clark Guy [mailto:guy.clark@sbt.siemens.com]
Sent: Thursday, August 08, 2002 3:08 PM
To: KAPETAC@polaroid.com
Subject: [filmscanners] RE: IV ED dynamic range... DYNAMIC RANGE!


HI, Constantine!

You are correct that if one adds uncontrolled  light scattering into the mix
of variables, one can obtain less reliablie results than if one eliminates
it.

I (for the purposes of discussion) chose to ignore scattering.   In my tests
at my old employers' labs, we used high quality  glass filters, and later,
when verifying the operation of our devices, we used high purity distilled
water (in highly polished quartz cuvettes)  with the appropriate dyes to
minimize the effects of scattering.

If a standard were created mandating the use of some particular type of
filter set for scanner testing, all of you would be using the same standard,
and your numbers would be comparable.

I still maintain that this can be done, and at miniscule cost to the
manufacturers of scanners. (compared to your advertising budgets, that is!)

Guy

-----Original Message-----
From: Kapetanakis, Constantine [mailto:KAPETAC@polaroid.com]
Sent: Thursday, August 08, 2002 1:49 PM
To: Clark Guy
Subject: [filmscanners] RE: IV ED dynamic range... DYNAMIC RANGE!


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.

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