Calculating Dev Times for new Kodak Films

With a view to the future for those of us who extesively use the Kodak films which are about to be changed and will have different developing times, I have the following question for those of you who are photochemistry experts:

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After finding a new developing time for, say, Normal Development for a specific film, say Tri-X Professional, is there any formula I can apply to arrive at my other development times that I have already calibrated for the older version of the film, e.g. N-1, N+1, etc.?

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More specifically, would applying the same percentage of change to the other developing times get me in the ball park, or is their some kind of proportional relationship that needs to be applied, or is there no specific relationship at all (in which case all the calibrations will have to be done again from scratch!).

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Thanks in advance for the expert input.

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Regards, ;^D)

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I

Doremus,

I wouldn't over-science this too much. Who's to say what N+1 is?

Apply some conversion factor and monitor the results. If you're not

satisfied, noodle the numbers a little.

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R

A simple multiplication factor should be more than accurate enough.

Just divide the new time by the old time to get the factor and then

multiply all your N+, N- times by that.<br>Say the old recommended

Kodak time was 6 minutes, and the new one is 7.5; then your factor

would be 1.25.<br>Multiply your own calibrated times by that, and you

should be close enough.<p>There are some published results that seem

to show there's a proportional relationship between the induction time

(time to first appearance of a visible image), and the development

time to a given density of ANY developer with ANY film. Whether that

information has any practical use aside from inspection developing is

another matter. This 'Watkin's factor' was used quite widely before

the time and temperature method became normal practice.