Digital BW, The Print

Austin,

First off I'd like to acknowledge you and Martin for the time you've put
into this topic. You both have gone far beyond the call of duty. Thanks.

Comments and questions below.
 
>> Earlier in the thread you have said (I'm paraphrasing) that the dynamic
>> range of a print is an expression of how many tones that print contains.
> 
> Basically correct.
> 
>> I don't see how the simple test you suggest, which only differs from the
>> more common test for dynamic range (or what you call density
>> range) is just
>> the additional step of measuring the variance across your test patch.
> 
> Exactly.  Since you can only discern by that value, that gives you the
> minimum discernable value.  How it differs is quite simple.  Density range
> does NOT take this into consideration at all.  It is merely a range between
> two static values.  Dynamic range is how many discernable values you get
> across that range.  Case in point is you can have a print with a high
> density range, pure black on a pure white background, but it has no dynamic
> range...no tones in between.
> 
>> I
>> don't see how that information tells you how many tones are in the print.
> 
> You can only discern what you can discern, and anything that can't be
> discerned is the same.
> 
> 
>> This would seem to be a case where, as you've said before, only 2 bits of
>> info is needed to establish dynamic range, no?
> 
> No, only two bits are needed to represent the DENSITY range.

I thought one bit could give you density range: maximum measurable (max
black), minus min measurable (paper white). Two tones, one bit. And that it
was the addition of the min discernable value (which I'll shorthand to
noise), which you sampled via deviation across the test patch, which gave
you the third component (noise) of your dynamic range equation?
 
>> But this then could suggest
>> the material is capable of a huge dynamic range, when in fact only three
>> tones are present.
> 
> No, huge density range, but very low dynamic range.

I'm confused.

I read you to mean that you get your dynamic range (I'll abbreviate that to
DyR from here on in this post) by measuring the min and max (I'm short
handing here, you know what I mean), subtract the min from the max (which is
your density range (DnR), then dividing that sum by your noise, which you
measured from your third tone. That gives you your DyR.

So you've sampled three tones, referred to as: min, max, and test (or min
discernable, or noise). Let's assume this print was comprised of ONLY these
three tones. You could calculate a very high DyR from these three tones,
implying the print has many intermediary tones, which it does not, no?
 
>> Furthermore, what does it say about a scenario where ones printer/workflow
>> happens to produce a certain granularity/banding/mottling/artifacting
>> precisely in the tonal region of your test patch, but nowhere else; or
>> worse, the converse, everywhere but your patch?
> 
> It's merely an example.  You can quantify your system any way you want.
> Those details are not relevant to the concepts involved that are trying to
> be discussed here.

Okay.
 
>> And what of all this inkjet artifacting?
> 
> We aren't talking about inkjet prints in this example...only chemical
> prints.

Really? First off I wasn't aware of that, when was that distinction made?
Second, so are you saying the two require different testing methodologies to
determine DyR? That's the first you've said of THAT.
 
>> Furthermore, I agree that there needs to be some term to
>> distinguish between
>> a litho-like substance, and a continuous tone substance, where
>> the two could
>> conceivably have the same density range, while one is capable of far more
>> shades in between. But I wonder now if dynamic range IS that descriptor,
> 
> It is.
> 
>> when in fact you could measure a three toned medium and presume it to have
>> the same number of tones and the continuous tone item, based upon
>> that test
>> and calculation. So, at best dynamic range can provide a
>> predictor of what a
>> medium is capable of, but it assumes a complete and linear set of tones
>> between the ends, which may or may not be so; at worst it could
>> mislead one
>> wildly.
> 
> Not at all.  Dynamic range can be measured/calculated as precisely as you
> like.  It's like measuring the width of a 4 x 8 sheet of plywood.  You can
> just say it's 4' wide, or you can take a measurement every 1' or every 1" or
> over any distance you want...  I'm just showing a measurement technique
> here...there is nothing about dynamic range, per se, in this plywood
> example.

I follow, but we can't proceed until we clear up my questions above.
 
>> I need to explore this subject of linearity more fully as it pertains to
>> dynamic range. For instance, a print with an expansion of highlights and
>> contraction of shadows (= high contrast) will contain fewer tones than the
>> material is capable of, but your measure of dynamic range will
>> not indicate
>> that has occurred. So, is dynamic range a measure of the number
>> of tones an
>> item contains, or a measure of what the material is capable of if perfect
>> linearity is present?
> 
> It entirely depends on what you are measuring and how you measure it.

Understood.
 
>> This has me wonder why you assume a Piezo print to have greater dynamic
>> range than a silver print given these considerations:
> 
> Because I have printed the exact same negative on both, and the Piezo print
> had more tones visible to the eye.

Okay, but that is one small sample, and without knowing your workflows for
both processes there is no way for anyone else to interpret that. But I
fully understand that in your tests you did better with Piezo.
 
>> A) We know a well handled glossy fiber print is capable of a
>> greater density
>> range than Piezo.
> 
> Which is not really relevant to dynamic range...

Okay, lets explore this. If DyR is the density range/min discernable value,
the greater the density range, the more noise the system can handle and
still yield a high DyR. (if your min discernable value is 1, and your DnR is
5 then your DyR would be 5/1 =5, if your DnR is 4 and noise is the same 4/1
=4. Like the extent of my math? <G>) So if two systems have equal noise, the
one with the higher DnR will have the higher DnR, no? That is the relevance
I'm speaking to.
 
>> B) We know the source material of a silver print (negative) is capapble of
>> more tones (millions? billions?) than the source material for an inkjet
>> print (256? 65,000?).
> 
> I don't believe we know that.

Well it's not a given in every case, but we know MOST people out here are
Piezo printing from 8-bit, 256 shade files, and I trust you agree most
continuous tone negative films are EASILY *capable* of containing more tones
than that. Tell me you don't disagree with that!
 
>> C) Noise can go either way, depending on which papers are used in each
>> respective system, and other workflow considerations.
> 
> Absolutely.
> 
>> I'm trying to get my head around my sense that the approach you
>> advocate for
>> determining the dynamic range of a print is only marginally more
>> informative
>> than the approach to determining density range (which is fine, you didn't
>> invent the formula <G>);
> 
> But density range only tells you the relative distance between the
> endpoints, and as we have discussed in the past, can be represented with
> only two bits...and as the simple equation for density range shows, it
> merely is (dMax - dMin) and is a static measurement.

Understood.
 
>> that measuring the dynamic range of a print still
>> doesn't tell you how many tones it contains;
> 
> It certainly does, as defined by the equation for dynamic range ((dMax -
> dMin) / smallest discernable value).  Note, it has an additional variable in
> the equation beyond what density range does.  The dynamic range of a
> chemical print certainly can be done as a range.  You can add any complexity
> to it you want...but it doesn't change the basic concept.

Okay, how many tones are in a print with a DyR of 25db? 10, 100, 1000?

Is it possible to measure a DyR of a print that contains less than that many
tones?, Say a print with paper white with a 95% reflectance, a dmax of 2.2,
a min discernable value of .1, and 10 solid shades of gray within the DnR?

What would that print's DyR be compared to a print with all the same
features but with 100 shades within the same DnR and noise parameters?
 
>> that I see no logic that a
>> Piezo print is any more capable of greater dynamic range than
>> silver,
> 
> It doesn't have logic associated with it, it's simply observation.

Okay, I'll let it go at that. ;-)
 
>> I told you this would be noisy/rambling. ;-)
> 
> You had a respectable dynamic range here ;-)

Lovely, you are kind, thank you!
 
>> Your thoughts please.
> 
> Anything else?
> 
> Regards,
> 
> Austin
> 
> P.S.  Please keep it short if you could...

I tried...

And thanks again.

Todd