And I still don't understand how one can interpret or apply CIs without knowing how they were determined. What points are chosen along the curve, for example. In any case I'm just along for the ride and enjoy Stephen's posts.
So using the method for determining CI found in Kodak's Sensitometry Workbook the curve used in the examples has a CI of 0.58. Close as I can tell.
The placement of the zones can be determined by the paper's range, if the papers printable range is 1.05 then B should print the zones as expected and A would end up clipping.
Am I missing something with regard to the paper's characteristics?
Mark, you are bang on in framing the problem! The average LER for a grade two paper is 1.05, as is shown in paper curve A of the "LER examples" attachment.
On page 220 of The Negative under the heading "Normal Development" Adams writes, "We must first establish the "normal" before we can depart from it in a useful way. Testing procedures given in the Appendix, or similar methods of determining optimum processing should be carried out and the results applied in practical photography to confirm their effectiveness. In general terms, I have found that approximate values for normal negative densities are about as follows:
Diffusion enlarger
Value I 0.09 to 0.11
Value VIII 1.25 to 1.35"
As the negative density range becomes the LER for the paper, the density range for normal conditions is from 1.15 to 1.25. I'm using the higher range in this thread.
Curve B in "LER Examples" illustrates how a NDR of 1.25 will print on a grade 2 paper with an LER of 1.06.
Obviously it doesn't fit. The print will appear dark and contrasty.
According to Loyd Jones, "the procedure followed in obtaining a relationship between DS (read NDR) and log ES (read LER) may seem forced and artificial. This we grant, and it must be borne in mind that the print quality obtained by its use will not be the highest possible quality. But what other course is there to follow? Either we must make the best of a somewhat imperfect relationship of face the prospect of having no criterion whatever for choosing the paper contrast grade."
He's saying that the matching of the NDR to the paper LER doesn't mean that you will have a perfect print. It's a very interesting topic in its own right and it has to do with psychophysics. Can an imperfect system of measurement be the answer? No. Even if it was a factor in this case, the difference between the two aim NDRs falls outside of the imprecision tolerances of the LER system. So even though the process doesn't guarantee the highest quality, it doesn't account for choosing such disparate values.
Therefore, a negative with a density range of 1.25 will simply fail to make a satisfactory print according to the LER criteria.
Problem solved. Question answered. Except that people aren't producing dark and contrasty prints with the Zone System criteria. And people aren't producing light and flat prints using the paper LER criteria to determine the aim NDR. They both seem to work.
How is this possible? How can this large of a discrepancy between the two aim values be reconciled with the all the supporting evidence that they both produce high quality prints?
Shifting over to the CI chart. What are the variables involved in determining those values? As CI is a form of slope / gradient, then the equation of Rise / Run = slope or gradient should solve it (Okay, I'm going to use the term "gradient" from now on). The chart gives both variables. Plug one set in and see.
Compare the CI chart to the processing information from the Xtol pamphlet. What does the pamphlet have as Normal? Where does that fit on the CI chart?
Last edited by Stephen Benskin; 09-09-2011 at 09:21 PM. Click to view previous post history.
And I still don't understand how one can interpret or apply CIs without knowing how they were determined. What points are chosen along the curve, for example. In any case I'm just along for the ride and enjoy Stephen's posts.
This is important stuff and deserves attention. Michael you should post this question in a new thread.
In the mean time, a little reading material.
Last edited by Stephen Benskin; 09-09-2011 at 09:00 PM. Click to view previous post history.
OK I drew the A and B on my own graph paper while you were posting the answer.
As I went along I just Knew A was a Negative. It just felt like I was marking down sensitometry results.
I couldn't figure out how B exactly hit 1.05. But now you explain it is the paper curve of a 1.05 LER paper. So by definition, it will hit 1.05.
I'm familiar with the Loyd Jones quote and the wheel used to pick a paper grade for a negative. Of course it is imperfect. The wheel can suggest a grade - then when you go to print, in the end, pictorially and psycophysically you might go up or down a grade, or burn or dodge to make the print look right.
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Originally Posted by Bill Burk
