[filmscanners] RE: Dynamic range

["Austin Franklin" <darkroom@ix.netcom.com>]

Roy,

> All the stuff about number of levels and resolution are artifacts of the
> digital process and not part of the DyR concept which existed way before
> the word digital was even coined.

I don't know if that is true or not, as I don't know who "invented" the
characterization, or when it was "invented"...I am trying to find out.  I
take it, for you to make this as a statement of fact, you know the actual
history of dynamic range?  Who "invented" it?  What's your earliest
reference of "dynamic range"?

I believe the concept of resolution is inherent in the concept of dynamic
range.  Whether that "works" for you or not, at least for me, and for many
other engineers I know, is an important understanding.

> >> In all the situations we're talking about, they are
> >> just plain one and the same.  Dynamic Range is a ratio AND its
> a range --
> >
> > Can you point me to ANYWHERE on earth that says something to
> the effect "we
> > have a dynamic range that goes from .01 to 3.2" or something
> like that?  No,
> > because dynamic range is ONE number, as clearly specified in
> EVERY dynamic
> > range equation.  It is NOT a RANGE of numbers.
>
> The ONE number is the SIZE of the RANGE.

Ah, yes...but that's not really a range, now is it?

> Yes, a range has a max
> and a min.

Woah, we have an agreement here ;-)

> But the SIZE of the range is ONE number

OK. (two in a row!)

> -- and it can be mathematically
> calculated with a subtraction OR with a ratio.  In the dynamic range
> case we always calculate the SIZE of the range with a ratio = max/min.

I see how size can have a merit (which is a relative ratio), and range, as
they apply to dynamic range.  Size in the fact that the largest signal is N
times larger than the smallest...and range in that you can say "all integer
values from 1:1 to N:1".  BUT...realize that "all integer values from 1:1 to
N:1" really denotes a resolution over a particular "range" too...that you
have N discrete values.

> You don't seem to have trouble when someone says "density range" and
> Dmax - Dmin.  Why the hangup when the adjective is changed?

Because dynamic range and density range are two entirely different things.
When someone says a "density range" of 3.6D, that means from, say, .2D to
3.8D, or whatever.  Within that range, you can discern ANY value you want at
any resolution you want, down to .0000001D if you could...but dynamic range,
in and of it self, has a number of "discernable" steps.  Density range does
not.

>   A specification of dynamic
> > range, say, 92dB, does NOT give you ANY range,
>
> Like I said it gives you the SIZE of the RANGE of power levels.

I'm fine with that.

> > So much for your promise to not post any more on this...

I'm sorry about that, and some of my other, snitty statement...I really
don't mean to be snitty with you...but you're just so damn prolific, and
repeating the same thing...and it gets tiring and frustrating...with nothing
(seemingly) new added.  This post was short and easy, and quite to the
point...which I'm happy to respond to.  If you can keep the posts short, I'd
be a lot happier.

Regards,

Austin

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