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



Austin,
I really don't want to dance, so I am not going to get into the "he said,
she said thing"

I am going to stick by my interpretation of what was said and how each of
you has interpreted it.  For now, I am not concerned with the "maximum
acceptable signal", given that I understand everyone's interpretation of
this to be the maximum amplitude short of "flat line" saturation (concept
mine).  I do not think anyone but possibly me is thinking in absolute terms
of theoretically possible maximum amplitude of the signal beyond stauration,
which may be unreadable or unmeasurable.  I think in everone's practical
case the notion of full saturation is the limiting case for maximum
accpetible signal.

However, turning to "minimum acceptible signal," if I understand you, you
are holding that theoretically the dMax-dMin range is much broader than the
dynamic range whose lower limit is limited by the base noise level and whose
upper limit is limited by the flat line saturation level.  In other words,
the dynamic range is the readable range (a subset within the full dMax-dMin
range) where the full range can theoretically extend beyond the dynamic
range such that they may or may not be synonomous or identical.

Julian, if I read him correctly seeks to define the dMax-dMin range as being
that which already accounts for the base noise on the lower dMin end and the
full saturation level on the dMax end; thus he is implicitly accounting for
the basic noise level without making it an explicit part of the equation.
Thus, his definition of dynamic range is the readable or measurable range
and for all practical purposes identical to the dMax-dMin range.  The
phrases, "...in one scan.  It is the instantaneous range the scanner can
handle," I take to be throw away phrases where he is for purposes of
simplicity and consistency with how specs are typically derived trying to
eliminate the possibility that multiple passes could very well alte5r and
extend the dynamic range by lowering the basic noise level on average.

Thus, I hear both you saying basically the same thing but in slightly
different words that include and exclude elements in definitions by
assuption and stipulation.  If I am wrong in my understanding of each or
both of you, then I do not have the foggest idea what is being said and
havve to figure that you are both crazy, leaving me the only sane one in the
asylum.  The King of Hearts always said that it was the rational sane world
of engineers that were the crazy ones with the only sane ones being locked
away in the asylum.

When we get done all the word games, we will find that we are all engaged in
merely an ecology of games that impact on each other but are separate and
distinct games that we are playing with ourselves such that we are all two
steps short of a twelve step table.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Austin Franklin
Sent: Thursday, August 08, 2002 4:27 PM
To: laurie@advancenet.net
Subject: [filmscanners] RE: IV ED dynamic range... DYNAMIC RANGE!


Hi Laurie,

> The whole damn thing turns on the phrase, "acceptable signal level."
> Austin, if I read him correctly, holds that "acceptability" is defined as
> being above the noise level at the low end;

If you read the definitions used, both "terms" used "acceptable signal
level".  When used as "minimum", it, to me, means noise, when used as
maximum, it mean the maximum amplitude of the signal (before clipping, or
saturating or whatever...where the signal is still valid).

> Julian probably implicitly
> accepts this also.

I do not believe this.  What others, who do not believe my understanding of
dynamic range, believe is that dynamic range is not based on noise, but on
the largest value of density the device can detect, minus the smallest
density value the device can detect, basically, dMax - dMin, and there is no
noise in the equation...  This is simply the density range, and is not the
dynamic range.

Here is what he said:

"DYNAMIC RANGE on the other hand, is the smaller range within the Density
Range that the scanner can capture AT ONE TIME i.e. dynamically i.e in one
scan.  It is the instantaneous range the scanner can handle."

Which, of course, has nothing to do with what I believe dynamic range is.

Austin

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