Differences of opinion are always best discussed verbally IMO. I can remember working with the assistant branch head on a report at NACA. we were in a conference room with the door closed. Others in the outer office heard much loud talk and thought we were at each other's throats. Then we would take a break, go to the Coke machine and flip coins, talk about sports, weather or what not, go back into the conference room and resume making noise. All I remember about the report is that it was an analysis of wing loads measured in flight on a flexible swept wing bomber. It got published.Patrick;
For the numbers you give, based on what we have discussed, you have to give a film and developer to match the data to. I too have reservations about the derivation of our fellow APUG member. I read it earlier and something bothered me so I did not post, but then you are better at math than I am I think.
Patrick, I truly wish we could meet or talk sometime. We have so much information to exchange.
PE
Here, if it goes through, is a chart of the type I have been describing, for APX 100 in Rodinal 1+50. Data read from AGFA chart.
That all makes sense, but it is really no closer to the original topic of the thread!
Have you tried figuring out the mathematical progression of temps on that secondary x axis? This info would be needed to construct a line from, say 19 degrees to the G-Max point (without adding additional empiric data for 19 degrees).
Congratulations on the grandchild!
Please note the severe difference in slopes of two of these, and the moderate difference with the rest of them. This indicates that the developers behave differently with temperature. In particular, note DK-50.
PE
Patrick,The very same data that I showed in graph form exists in the form of a spreadsheet produced by the computer program that I wrote some years ago. I have tested the program on the J-109 data and found quite good agreement. I enter three values of CI from J-109 for a particular film (I keep thinking I already said this) and the program computes the other values in that particular spreadsheet. If you would like, I will be glad to e-mail the program. It's only about 50 K. It runs directly on MSDOS machines. I shall try to show a sample of what it prints out.
Patrick,
I believe you usually use Rodinal 1:50. Is that the dilution for this data.
Thanks,
Lee
Yes. The data were from AGFA, in the form of curves showing time vs temperature for fixed CI of .55, .65 and .75. You would never suspect by looking at the raw data that you coud get such an orderly plot or spread sheet, but you can see by the graph that the lines derived from the AGFA curves also fit other data points that were not used in deriving the result.
Great!k(T) is the slope on semilog paper of the line of constant 75 degree temperature. Take the ratio of 2 such slopes, divide that number by the temperature difference, and the log of that number is C. It is supposed to make interpolating or extrapolating new temperature lines "easier".
Sorry fro the late entry here, but I have a calculator at Dead Link Removed. I'll dig up the formula I used. and post soon
TR
Correction: ..photographers in the days of Speed Graphics loved DK-50...
Also, ...DK-50 has a much different response to temperature change than average of other developers.
Hi, Just curious about the source of the graph - I have the 7th edition of publication J-1, and it doesn't have the temperature graph.Here is the plot of several Kodak developers as a function of temperature, with the film held constant and the time of development is that which gives the closest match to speed and contrast in all cases.
It is taken from the Kodak Advanced Technical publication J-1 "Processing Chemicals and Formulas for Black-and-White Photography".
PE
He says the same in the 6th ed. (1946) and every edition up to the 17th. (Good we have archive.org) But than in the 18th (1972) edition he gives the same coeficients but for 10 °F (or 6 °C, as he mentions 2 pages later). I wonder what the reason for this is. It is a huge difference.
https://archive.org/details/cu31924015369055/ page 72:
"The increase in speed of development with an increase of 10°F is taken as the Temperature Coefficient of the developer. For example if we find that a particular developer works twice as quickly at 75°F as it did at 65°F then we say that it has a Temperature Coefficient of 2. The following table gives a rough guide to the time-temperature relationship of the three main types of developer, assuming Temperature Coefficient of 1.8 for standard MQ developers, 1.6 for fine-grain and 2.3 for super fine grain developers."
and on p74: "Thus, each developer has its own Temperature Coefficient. Nevertheless, for most practical purposes, this can be taken as 2. That means that development time should be halved for each 10°F (6°C) rise in temperature."
He repeats that in the 18th revised edition from 1980 https://archive.org/details/DevelopingTheNegativeTechnique/ p. 72 and 74.
The thing is, he has the same factors for 32 years referred to a change of 10 centidegrees. Than suddenly after 16 editions the same factors should be applied for a change of 10 °F, altough he himself says this change represents a significantly lesser change in energy.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?