Digital BW, The Print

Roy,

> > Is it possible that *some* people used the term dynamic range
> to describe
> > something one step more complex than density range? I think
> behind Austin's
> > absolutist rhetoric that is what he's saying.
>
> Hi Todd,
>
> I believe that other than Austin being an instance of "*some*
> people", no-one
> uses the term like Austin.

You say that, but it isn't true.  In audio, dynamic range IS clearly more
than just the range of the highest voltage to the lowest voltage, Higgins
clearly shows that.  Dynamic range IS more complex than density range for
imaging, and the equation for dynamic range and density range clearly show
that.

> But I really think if Austin is claiming "there are others" he
> ought to be able
> to cite a couple.

I have, but you interpret their words as meaning something else.  Even
Higgins states what I say...but you claim that because he uses the word
"audio", even though it is clearly listed as an "EXAMPLE", and happens to
use audio, that what he says is only applicable to audio.  That's a
misinterpretation.

> Correct me if I'm wrong but I'm asked for a
> reference many
> times so far and they don't seem to be forth coming.

Again, you say that, but it's not true.  I've given references.  You just
claim that they aren't applicable, or claim that they mean something
different than I say they do.  Sigh.

> On the
> other hand I've
> cited some fairly noteworthy people that agree with my interpretation.

Noteworthy in something, but not noteworthy in engineering or signal
processing.

> I
> really don't think its a "I SAY" versus "HE SAYS" issue.  I'm
> just the messenger.

That's my line...I didn't make up the dynamic range equation, it IS what it
IS, and it clearly, by the actual equation, is not the same as density
range.

> I think it is a IMAGING WORLD SAYS versus AUSTIN SAYS issue  -- and since
> that may not to obvious I'm trying to show that.

Well, as I've said, your references are not engineers or really in-depth
technical people, they are primarily Photoshop gurus.  From what I can tell,
none of them have ever designed any imaging equipment.  How would they know
what dynamic range really is, or that what they are told is right or wrong,
or what is the significance of what they are told?

> Just to reclarify a little:  Dynamic range is the range of useful
> light values or
> their representation in an Image.  Range is defined by a Maximum
> and a Minimum.
> Describing  the range is the max and min, the size of the range
> would be the difference.

Yes, range is defined by max and min, and since the range you are defining
IS a range of density, all max and min gives you is the DENSITY RANGE.  It
does not give you the dynamic range, as clearly shown by the dynamic range
equation.

> By "useful" (I liked Ansel's use of this word) I mean there may
> be light values
> too dark or too bright to discern any information.

That's called thresholding.

> In photo
> language high values
> that are blocked up or shadows that have no detail are NOT useful and
> would not be included in the Dynamic Range.

They would not be included in the DENSITY range.  Since they are outside the
density range, of course they have no dynamic range.

> When you get to the scanner, you've its DyR has be at least as large and
> its min thru max has to completely cover the DyR of the image on film.

Not right, it's DENSITY range that has to cover the DENSITY range of the
film.

dMax and dMin in the real world scene are simply represented on film by
"some" dMax and dMin of the film, that is not at all calibrated to the real
world.  Same with scanning and then printing.  You can scan film that has
one dMin and dMax, and then print it, but the values you get out are nothing
but relative value to each other, they in no way bear any resemblance to the
actual measurable dMax, dMin values that are on the film.

You can print a negative with a density range of 1 and another negative with
a density range of 2, but get a print density range of 2 for both negatives.

> Again here DyR of the scanner is measured in density

Dynamic range is never measured in density, it is measured in dB.  There is
a reason for that, simply because dB shows how much is there, as opposed to
density range which doesn't say a wit about what's in between.  Dynamic
range is a property of the "discernability" of density.

> The staircase model seems so perfect
> I'd like to keep pointing back to it.

Yeah, but your belief of what it represents is mistaken.  The bottom step is
dMin, the top step is dMax and the number of steps is the dynamic range (and
in the digital world, also the bit depth).  This probably got misinterpreted
because someone, sometime, used a staircase example to try to describe
dynamic range to someone else, who didn't quite understand it...etc.  Kind
of like telephone.

Obviously you want to believe what you want to believe, and/or just don't
want to understand what dynamic range really means.  I know you believe you
understand it, but from what you cite, you don't.  You use references that
don't understand it themselves, and when I cite references that are quite
technical, you either ignore them, or misinterpret them.  I know you can say
that I am misinterpreting them...but I HAVE designed imaging equipment, and
audio equipment, and subjected my self to PROFESSIONAL peer review.

You are obviously an excellent photographer, as I've visited your web site,
and find your work to be outstanding.  Perhaps it might be useful if you
stated what your background is that is applicable to this discussion.  You
said you have "a couple of degrees in EE", but haven't said at all what your
"field" is (or was), or if you've actually done any applicable design work,
or used the concept of dynamic range in any of your work.

You've never answered what is "dynamic" about YOUR belief in what dynamic
range means.  I believe, there is nothing dynamic about what you believe
dynamic range is, and I believe dynamic makes perfect sense when applied to
what I say "dynamic range" is.

Austin