[filmscanners] RE: Density vs Dynamic range

["Laurie Solomon" <laurie@advancenet.net>]

>Dynamic range is, in our case, (dMax - dMin) / noise.
I guess I tend to want to stay away from that definition in part because I
am not really able to visualize it very well; but I can visualize "Dynamic
range is the number of discernable values within a density range (in our
case)" much better so I tend to favor this definition over the other.  Just
a case of my limitations getting into the act. Sorry. :-)

>Well, you HAVE to increase the scanners dynamic range for more bits to
>increase the ability to represent accurately the value coming from the CCD,
>assuming, as I've said that the number of bits was matched to the dynamic
>range of the CCD in the first place.

>Doubling the number of bits also does not increase the density range of the
>scanner, and it also doesn't increase the ability to represent accurately
>the dynamic range (as I said above)

Alas, you are beginning to lose me because of my limited technical
engineering knowledge - I suspect - with your first paragraph. With respect
to the first part of the second paragraph, I understand what you are saying
and I agree, for what it is worth.  However, my understanding and agreement
with the second part of this paragraph may turn on the terminological use of
the notion of "accurrately."  If I understand what you have been saying, I
can see that the number of bits has no bearing on "accuracy of
representation" in the literal corrspondence notion of truth sense; but in a
more figurative sense where the terms "accuracy of representation" stand for
ability to define the density range in terms of finer gradiations or more
descrete segments, I would suggest that it does increase the ability to
discern and designate finer differences within the the density range.

Unfortunately, I think the confusion stems from your desire to use the key
terms in their very precise technical sense as defined in engineering
formulas and concepts whereas I am only able to really grasp the general
theoretical sense of the concepts in more metaphorical meanings.
Nevertheless, I really appreciate the time everyone is taking to nurse me
along in my attempt to decipher the discussion.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Austin Franklin
Sent: Sunday, June 09, 2002 10:15 PM
To: laurie@advancenet.net
Subject: [filmscanners] RE: Density vs Dynamic range


Hi Laurie,

> The first point of confusion in your discussion with Austin appears to be
> that what you are referring to as "dynamic range" he is referring to as
> "density range" or that you are using the two terms synonomously
> while he is
> using them as naming two different concepts.

Dynamic range is, in our case, (dMax - dMin) / noise.  Density range is
simply dMax - dMin.  Dynamic range is the number of discernable values
within a density range (in our case).  Density range is simply the max
density value you can get minus the minimum density value you can get.

> For instance, if I may take
> the liberty to put words in his mouth, take the statement:
>       "If we double the number of bits (possible values) that doesn't
>       increase the dynamic range of the scanner, only it's
> ability to represent
>       accurately the value coming from the CCD."
>
> I think apart from maybe disagreeing with "the value coming from the CCD,"
> he would say that what you are saying should read:
>       If we double the number of bits (possible values) that doesn't
>       increase the DENSITY RANGE of the scanner, only it's
> ability to represent
>       accurately the DYNAMIC RANGE value CAPTURED AND DIGITALIZED by the
>       scanner's analog to digital converter.

Well, you HAVE to increase the scanners dynamic range for more bits to
increase the ability to represent accurately the value coming from the CCD,
assuming, as I've said that the number of bits was matched to the dynamic
range of the CCD in the first place.

Doubling the number of bits also does not increase the density range of the
scanner, and it also doesn't increase the ability to represent accurately
the dynamic range (as I said above).

> (Austin, if you are reading this and I am putting the wrong spin on it or
> words in your mouth, please feel free to correct me.)

Yeah, I think things are being confused a bit (sic ;-)...  Too bad ;-(  It's
really quite simple.

Regards,

Austin

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