Please show me any two film/developer combinations in the chart the have the SAME baseline time at 20c and have DIFFERENT times at 18c based on the wheel and chart!
Here.
From the 1962 'Negative Making' booklet from EKC,
showing Plus-X sheet film. This IS representative.
In the Darkroom Data Guide, the Development Dial # for D-76 is 34, for DK:50 1+1 is 34, and for Microdol is 40.
The Development Dial follows the D-76 curve: 68˚ is 8', 75˚ is tad under 6'.
For DK:50 1+1, the wheel and curve chart agree at 68˚, 6'. The wheel specs 4 1/2 minutes for 75˚ while the chart suggests 5'.
The wheel and chart call out 10' for Microdol at 68˚. At 75˚, the dataguide wants 7 1/3; the chart, 7 3/4.
All in all, the D-76 curve is useful for most film and developer combinations, but ACCURATE for none other than D-76 ! Other films show more dramatic differences, but this shows how it works.
The last published temperature adjust charts Kodak published, as far as I know, was in 1962; by the 1967 the charts were absent from the film booklets and the calculator wheel was in the dataguides. The assumption, and specification, was the dataguide was a starting point.Kodak ALSO published more specific data in table form. Until the advent of TMAX films, the published data was taken with a grain of salt. By the time XTOL was on the market, the data from EKC was dead accurate. A lot had changed, in particular, the state of the darkroom was closer to Lab quality than before. But it is just possible there was a different attitude in behalf of EKC.
The Dataguide, and Development Wheels are valuable, but they seem to follow the 80/20 rule. Assigning a precision to them which they were never intended to possess would be a mistake.
My observation over the years was that Kodak's old data was to get you CLOSE, and SAFE.
Beyond that, you were on your own. |