Digital BW, The Print

Hiiiii again Martin ;-)

> Since Ansel Adams and Minor White worked out the zone system and by
> definition of the term dynamic range

Do you have a reference for EXACTLY what you claim?  I AM a Zone boy (as in
I do all Zone work, with development compensation etc.), and I see that the
Zone system has some basis in dynamic range, simply by defining 10 steps,
that's giving it SOME dynamic range...

> From NASA website:
> From the Cornell University Library:
> From Digital Photography Review:

And you conveniently left out the ones that were "better" ;-)  Why do you
keep going back to taking some one's interpretation of a REAL EQUATION and
not just use the real equation?  Talk about adding noise to the system!

> > It does not, except for using different multiplication factors for other
> > reasons, but it is ALWAYS based on (largest signal divided by smallest
> > discernable signal).  Always.
>
> But the determination of what is the meaningful largest and
> smallest signals
> is dependent on the system.

It is defined by the equation...we are going around in circles here...

> > > I understand that you don't agree with this
> > > and see it as a universal concept. What I am saying here is let's
> > > apply your
> > > equation to a photographic print and see if the values help us
> understand
> > > what we see.
> >
> > Well, I have and it does ;-)
>
> You have not been able to supply a value for the noise in your
> equation yet
> so how did you manage that.

Er, yes I did.  I gave you an example using 0.01D as the "noise".

> > > > OK, then how does only using dMax and dMin give you
> anything dynamic?
> > >
> > > They tell you the size tonal space you can change tones in and
> > > they tell you
> > > the size of the largest change you can make.
> >
> > That is density range, not dynamic range.  Why on earth does
> the equation
> > for dynamic range (the ONE AND ONLY one that anyone has presented, and
> given
> > a succinct reference for, namely the one I provided) clearly
> base dynamic
> > range on smallest discernable signal?
>
> Austin, that is simply not true. I have provided several of
> descriptions and
> definitions of dynamic range from several sources. I have taken those an
> written equations based upon the definitions. You simply say they
> are wrong
> because they do not match your equation.

You can NOT take someone's interpretation of an equation and just write the
equation from that!  My God.  As I've said a dozen times, and you, for some
reason won't get it, the dynamic range equation IS the equation for dynamic
range, period.  No matter how many times some pedestrian has tried to put
verbosity to it to try to describe it TO LAY PEOPLE using ambiguous terms.

> (snip)
> > > Okay, what would be a reasonable number of samples and which
> > > tones should we
> > > look at first?
> >
> > This is completely irrelevant to the overall discussion.  This is purely
> an
> > implementation issue.
>
> Austin, I offer you a chance to look at what might be the noise value of a
> print to use in your equation and you tell me that is irrelevant to the
> overall discussion? If you cannot give this term a value than how can you
> determine if your dynamic range tells you something significant about a
> print?

The point is there IS noise, it exists everywhere.  We do not have to
quantify it to know it exists.  It is also not a far stretch to believe it
is significant, knowing the difference in reflectance that paper has alone!

> > > Now I am confused again. So what attribute of the print would
> you use to
> > > determine min and max if not the whitest white and blackest black
> >
> > Good!  Confusion IS good...  Seriously.  OK, in the density range
> equation,
> > "max" IS simply the maximum density value you can measure by direct
> > measurement, and "min" IS simply the minimum density value you
> can measure
> > by direct measurement.  Simply put, measure the darkest patch, get your
> max
> > value, measure the paper, get your min value.
>
> Austin, I have been saying that for post after post. What else could the
> Dmin and Dmax of a print would be?

We are not in disagreement on how to derive the density range...and that
wasn't the important part of what I was saying, the next paragraph is.

> >
> > For dynamic range, take dMax (from your density range measurement) and
> > subtract your dMin (from your density range measurement), and that gives
> you
> > "max" for the dynamic range equation.  "min", basically, will be the
> > variance across the patch that I've suggested above.
>
> Okay, looks like the density range (or the log expression of ratio of the
> reflectance) divided by the noise.

YES.  Grrr.  As you said, and I quote: "I have been saying that for post
after post." ;-)

> Okay that is the X-Rite 810's uncertainly when it measures
> density but it is
> much better at this than the human eye. Like many instruments it is only
> linear over a specific range. This may be the case with our eyes
> as well but
> believe me the human eye has a tough time discerning tonal
> differences above
> 2.4.

I agree completely.

> > > Doesn't that suggest that the ability for the eye to discern
> tones is a
> > > function of the tonal density?
> >
> > Of course it is...but I don't see how that applies.
>
> Just that it varies from light to dark so that you could not take a simple
> seperation between discernable tones but would need to mathematically
> account for this variation.

Sure, but again, that's just an implementation detail ;-)

> > > What would the equation look like then?
> >
> > Don't know, I'd have to work it out...but as I've said, this is a red
> > herring and completely irrelevant to the overall discussion.
> It is merely
> > an implementation detail.
>
> If it can't be implemented what good is it?

Who said it can't be implemented?  Not I!

> If you don't have the
> values you
> need to apply your dynamic range equation, what use is it?

Having a "correct" value or not doesn't mean it doesn't exist!

> And this had nothing to do with the operator but only the materials. <G>

I was a VERY good B&W printer in the darkroom.  If it did have anything to
do with operator, it was negligible.  I was a real purist, with very good
equipment (still have it BTW, need to sell it ;-) and knew how to use it, as
I do my scanner.

Do you ever sleep?

Austin