I hope that you recognize one thing about this discussion. It is that you have chosen to move it into an arena apart from what my original response and all subsequent responses have said. You are the only one who is placing the qualification of all things "being equal" into this discussion.
Originally Posted by Photo Engineer
That is the basis of the disagreement that we have. Pt-pd and Azo are not the same as all other papers. I think that you will agree to that. You are making a global judgement based upon a limited view of things.
I will agree that if all things are equal that certain conditions will exist...but in this case all things are not equal.
Donald: I went back over this thread (much more compelling than going back outside to dig the drainage ditch around our house even deeper. The PNW is flooding. AZ sounds really good right now :-) The silver gelatin emusion that I (and PE) have been working with doesn't enter the paper in the same way as pt/pd or the salted POP types. When it is applied it looks like white jello - still warm and thin enough to flow. Even though it sits on the paper's surface, it is very durable. I haven't had any peel off or scratch (though I tend to be a tender technician). It is just thin enough to allow the texture of the paper show through. A print coated on baryta paper is very smooth, but the emulsion can be coated on all textures, greatly influencing the character of the final product.
Donald, I am quite familiar with the characteristics of Azo paper. After all, one of my emulsions is a very close duplicate of Azo. I am therefore in a position to state that I have coated the experiment I describe above and can verify that Azo exibits the characteristics that I describe if the curve is controlled as I describe. And, due to my familiarity with a number of other papers, including color, which I have coated, I can say that they all behave the same within their own class and even cross compared if they are made to equivalent curves.
Originally Posted by Donald Miller
The result is limited due to physics and we cannot get around the natural laws involved.
I too love the character of Azo and Pt/Pd, but they behave according to the same laws of reflectance and transmission and can be cross compared under the conditions I have described.
But, again, I say use what works. That is the underlying theme of everything I propose.
I think the first problem here is that "tonal scale" isn't really a precisely defined term. My understanding is that "tonal range" may be more appropriate and is sometimes used here as well. But even then, that term seems not to be well defined.
Originally Posted by Donald Miller
The 3rd edition of The Focal Encyclopedia of Photography doesn't have an entry for "Tonal Scale" or "Tonal Range." They do use the term "Tonality" and define it as, "The overall appearance of the densities of the component areas of a photograph or other image with respect to the effectiveness of the values in representing the subject."
Please correct me Donald, but I think this is what your question is about:
"Why is a higher print d-max necessary to achieve a print with greater Tonality?"
If so, then let's look at a print that has a density range of 1.5 (maybe a pt-pd print) and compare that to a print that has a density range of 2.1 (maybe an Azo print). Remembering that one stop of reflection density is equal to 0.3, our pt-pd print can reproduce a range of tones that will be compressed into a reflection density range of 5 stops, while the Azo print will reproduce a range of tones that will be compressed into a range of 7 stops.
This pt-pd print will only be able to display a "shorter" tonal range than the Azo print, which comparatively will display a "longer" tonal range. So the Azo print will have greater Tonality than the pt-pd print.
Back to our definition of tonality - "The overall appearance of the densities of the component areas of a photograph or other image with respect to the effectiveness of the values in representing the subject." Note the part about effectiveness of values in representing the subject. That means our eyes have to take part in this question.
Since our eyes can can't really get much more information out of a reflection print with a greater density range than about 2.1 or so, we can't really get a print that can display a greater range of tonality than really around 7 stops.
Using Zones as a reference - we probably can agree that there are 9 or 10 zones that can be reproduced in a print. The photographic process does this by compressing the tones. It's the toe, shoulder and overall contrast of the paper and films characterisctic curves that work to our advantage. They compress highlight and shadow densities from the original scene so that they can be reproduced in the range of tones that our printing paper can reproduce.
Even a material with a relatively low dmax like pt-pd can reproduce a wide range of tones - all 10 Zones even, but it can't do so without reproducing those tones at a reduced visual contrast. It does so by compressing even more than a paper with a greater density range. And of course, if a negative gets a minus development, it can allow the reproduction of more Zones, but again it must be at a lower overall print contrast.
Whether this meets our need for "effectiveness of the values in representing the subject", is the question to ask next.
Sharpness and resolution are primarily determined by paper surface. The water color and drawing papers we use with Pt./Pd. are simply not able to show much more than 10 lppm, if that. The paper texture simply breaks up any detail or resolution over 10 lppm. Silver prints on glossy papers, on the other hand, are capable of showing resolution well over 40 lppm.
My carbon prints placed on art and drawing papers do not show nearly as much detail as an image from the same negative placed on a hard surface, fixed out photographic paper.
Bear in mind, however, that the limit of human resolution is below 10 lppm for the great majority of persons.
Sandy, I have comparisons on 3 paper surface. I would agree that the ordering is as you say, but I have no numerical values at this time. However, I would like to add that the resolution depends on whether you are using a positive or a negative resolution chart.
One is a measure of fill in and the other is a measure of bloom in resolving power. These two numbers represent the extremes and should be taken into consideration with any material.