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[filmscanners] RE: Density vs Dynamic range



Julian,

> Julian said:
> > > Austin's number = (max - min)/noise
> > >          = (max-noise)/noise     [here]
> > >          = 8,599/1
> > >          = 8,599
>
> Austin replied:
> >I am very sorry to say, but you are playing games.  I have CLEARLY stated
> >that you are using the equation incorrectly, and you chose to
> ignore that.
> >That is dishonest.
> >
> >The CORRECT use of the equation is:
> >
> >                 = (max-MIN)/noise
> >                 = (8,600-0)/1
> >                 = 8,600
>
> Now this wasn't being dishonest, it was my *honest* attempt to interpret
> things the way you do.

Julian, how can that be?  First off, I have NEVER "interpreted" things that
way, and second, I HAVE CORRECTED YOU on this...numerous times...yet you
continue to misuse it.   It comes across, to me at least, as disingenuous.

> I wrote this based on your previous post which
> seems  to be different - here it is again:
>
> Austin said some time ago:
> >The mistake is you are using noise as your divisor instead of min signal
> >level. Your equations should be:
> >DR = 10log10(max-min)/noise)
> >where in case 1, range = 1-1000mV, noise 1mV so 1000-1 = 999/1 = 999
>
> Do you see why I am confused?

No.  I do not see why you are confused in this case.  I SEE what the mistake
you are making is, but I do not understand WHY you are making it.  In this
case, the minimum signal level and noise have the same value.

> Can you tell me which of these two uses of
> your equations is correct?

It is NOT my equation, first off.  All the equations shown ARE IDENTICAL, if
you understand simple mathematical properties.

> And can you tell me again, how you define this
> MIN?

"MIN" what?  Minimum signal level, or minimum discernable signal?  I have
clearly defined them both in my term definition post.  If not, refer to the
diagram I provided and the term "smallest" listed on the diagram is "minimum
discernable signal", which can also be noise, and "minimum signal level" is
the bottom line, at the top of the hatching, that the bottom of the arrow
for "largest" points to.

> Is MIN = noise, or is it zero?

It depends on which "MIN" you are talking about.  In one example, "minimum
signal level" is clearly stated to have a value of 1mV, and "minimum
discernable signal" is ALSO clearly stated to have a value of 1mV.

In the very top example, "minimum signal level" is CLEARLY stated to be 0
(as a range of 8600 means 0-8600, and has a "minimum signal level" of 0, and
a "maximum signal level" of 8600.  I believe that should be "simply"
obvious.

> Why?  Why is it different in these two
> examples?

Simply because "minimum signal level" IS STATED to be different.

> If MIN = zero, why?  (since this signal level is impossible).

How is it impossible to specify a signal range starting at 0, no matter WHAT
the noise/minimum discernable signal is?  It absolutely IS possible.

> You can see why I have had a problem interpreting what you are saying I
> think.

No, I don't see the problem.

> I am not saying you are WRONG, but I am saying that from where I
> sit, these two posts of yours are contradictory.

I see YOUR use of them contradictory.  It APPEARS you claim that a "range"
can not be used to derive "MAX", which I claim is the same as ("maximum
signal level" - "minimum signal level"), and for some reason want to
consider them differently.  I simply to NOT understand that, as it is a very
basic mathematical property of equivalence.

> Obviously they are not
> contradictory to you, but to me they are.  So without getting steamed up,
> can you just explain to me what is the difference betw these two, given
> that in both cases the minimum of the range is determined by noise.

No, "minimum of the range" is NOT determined by noise, though it CAN be.
Noise IS noise.  You can simply have a range of 5-10, with a noise of .01...

Answer me this.  When an A/D specs an input voltage of +-3V, what do you use
for your "MAX"???

> Or have you changed your view of what the top of this equation means?

That's the interesting part, my statements and views have not changed one
bit, yet your examples come to the exact same results as I have been saying
all along, IF you do things correctly.

> It is a pity you won't continue,

I will continue IF you don't go changing equations to make them wrong, when
they are not.

> especially since, as you have
> done before,
> you seem to be using this as a reason NOT to reply to the hard bits of my
> post.

There are no "hard bits" of your post, except those where you change about
the meaning and use of things I have clearly stated, and then claim they are
wrong.

> I really wish you would reply to ALL my post, even when the answers
> may not please you.

I HAVE responded to all your posts, but I am not going to respond to a
lengthy section that is based on a completely wrong premise.  There is no
need for me TO respond, as the entire section is incorrect.

> Sorry Austin - that you think I have been dishonest.  I may have been
> confused as to what you are saying, and I think anyone, engineeringly
> literate or not, would have been equally confused by your apparently
> self-contradictory statements.

They are certainly not self-contradictory.  You are changing them, and
reinterpreting differently than they have been stated, and you MAKE them
contradictory.

> I admit to
> believing that I am trying to accommodate myself to a moving
> target in this
> argument, as you *seem* to constantly change your mind.

Excuse me?  This, again, is entirely disingenuous.  I have NEVER changed my
mind, I HAVE clearly stated the terms I am using, and I have NOT wavered one
bit from my initial statements.  Period.

> I really would like you to address what I wrote yesterday on the examples
> of the log amp and the detector system.
> Otherwise it is too easy to draw
> the wrong conclusion as to why you won't address them.

I have addressed it, but you conveniently ignore that.  I agreed with you
that the dynamic range of that system is not solely based on noise, as it is
a non-linear system.  I also said that that example does NOT apply to film
scanners, as these are linear systems.  That example has NO bearing on this
discussion at all.

> As you can tell, I find your discussion is still hopelessly confused in
> terms of its definitions.  Can you please on one piece of cyber
> paper, that
> is in one place, define what your terms are:
>
> Maximum signal
> Minimum signal

I have already defined the terms I use VERY clearly.  Your terms above are
ambiguous, and not terms I am using.  There ARE NO COMMONLY DEFINED TERMS
related to dynamic range.  Every book and reference I've seen uses different
terms.  This is why I took the time to CLEARLY define the terms I was using,
so there was no confusion, and there wouldn't be if you simply read them.

> And can you relate these to minimum discernable signal and noise?  Please
> draw on your celebrated diagram what this minimum signal is, because it
> apparently is not what you call "smallest",

I do NOT call anything "smallest" as it is an ambiguous term.  The term
"minimum signal" is ENTIRELY AMBIGUOUS, and your use of ambiguous terms
allows you to continue "being confused".

Since you are talking about "minimum discernable signal" and "noise" in the
above paragraph, I will assume that is what YOU are have called here "what
this minimum signal is".  "minimum discernable signal" and "noise" are
labeled on the "celebrated" diagram as "smallest", and are both the "same"
in this case, since the system we are discussing (film scanner) is limited
by noise.

<snip the rest>

Look, Julian, why do you simply REFUSE to read the terms as I have taken the
time to CLEARLY defined in another post?  YOUR TERMS ARE AMBIGUOUS.
"smallest signal" can be interpreted to be one of two things, and I will NOT
use that term.

YOUR term "smallest" and "Minimum signal" can be either "minimum discernable
signal" (same as noise in our discussion, as we are discussing film
scanners) or "minimum signal level" (offset as you call it, which I am fine
with).

YOUR term "Maximum signal" can be either "maximum signal level" OR ("maximum
signal level" - "minimum signal level").

Again, the terms YOU are using are ambiguous.  This is why I have taken the
time to separate your TWO ambiguous terms into FOUR clearly defined terms,
so there is no confusion...BUT YOU continue to use your ambiguous terms,
well, ambiguously.

Austin

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