Digital BW, The Print

<snip>
> 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.

Austin,

I'm snipping from two separate posts to conserve space.

This is the linearity issue which I'm having trouble to get a handle on.
Doesn't DyR expressly assume that the component (scanner, monitor, paper)
has the capacity to delineate all tones within it's range pretty much
equally (linearly)? For instance it is assumed a scanner is able to discern
tones of similar difference equally across it's density range? (I would
assume that is what the pre-calibration is for, to linearize the A/Ds
conversion to the spectral output of the bulb.) With that assumption when
you say "dB shows how much is there, as opposed to density range which
doesn't say a wit about what's in between." it means that you can assume
that all of what's in between is represented equally, or at least capable of
being represented equally.

What I'm getting at is what does your DyR formula tell us about a print on
litho paper, which has a great range, but few tones between? (For the
purpose of this discussion lets not look at litho as being only pure black
as pure what, lets assume it has at least 2 dark shades and 2 light shades,
but no midtones.) It's not "noise" that is diluting it's intermediary tones.
So how will your formula describe, or account for that characteristic?

Furthermore, in the case of a scanner, "noise" only needs to be considered
in the dense regions of the film, right? Why is that? Would it be because
that is the only area in which it is of a significant value? If "noise" (I
have to keep it in quotes until it's defined (sigh ;-))) were as irrelevant
in the dense regions of film as in the thin regions, could it not similarly
be considered irrelevant, and thus dropped? Couldn't that be the case with
photo paper, noise is dropped leaving DyR as dMax - dMin?

<Snip>

Todd wrote:
>> So just when are you going to define "noise" WRT to a silver print and an
>> inkjet print so that we have a basis to judge whether it's existence is
>> RELEVANT?

Austin wrote:
> We have shown how to do it with inkjet prints with pretty reasonable
> certainty, and shown some proposed methodologies for doing so with chemical
> prints.

My apologies. Please restate it (copy and paste is fine) because all I
remember you saying is that you would take a few samples of a single tone
that lies within the range. I don't recall you giving the noise you are
measuring a name. You may have done so, but I lost it.
 
>> Please stop skirting that issue.
> 
> Well, I haven't!  Both Johnny Brownlow and I HAVE spoken to this issue.

Please see above and bottom.
 
>> Let me phrase it with a question: what is the analog
>> equivalent of a
>> bit?
> 
> It depends on what you are representing with that "bit" (voltage,
> current...), what the range of values can be, and what the noise is in that
> "system" (determines how many bits are needed for the A/D).

If you would be so kind, I'd *really* like to keep the discussion focused on
conventional photo materials for a while. See below.

At this point I think it would be extremely helpful if you could summarize
what you are still contending, or not, about what dynamic range as it
relates to conventional photography. Sometimes it's a tone count, others
times not. Sometimes it's expressed as db, others not. And you've still yet
to define noise (that I can remember, only that you would sample "it"),
which is the part of your equation that distinguished DyR from dMax - dMin.
That is simply too critical a concept to skimp on.

You must admit, the bent of your argument is really based upon an
electronic/digital orientation, and you really don't address the questions
that relate to analog-output/contone/conventional-photography with equal
vigor - which is the only place you've encountered disagreement from anyone.
So it's really hard to gauge where you stand on those issues.

Sorry, but I just think it's helpful if we each regroup from time to time so
we are clear on what the other person is still holding as a conviction and
what they've dropped. I did it myself earlier in the day and asked for your
response but none came. I'd hate for some of us to be in agreement and not
know it. ;-)

Thanks,
Todd