Response to Time Temperature compensation factors

I've looked at charts and times over the years and it seems that there is not a universal set of multipliers for all developer + film combinations. You can see this on, say, the Agfa data sheets where the graphs of dev times for various films show different gradients as a function of temperature, even for the same developer. I have an equation that I worked out from Kodak charts for HC-110. My dev time at 20C was 6 minutes for Tri-X, and the time d for different temperatures t (deg C) is: 59.4*e^(-.1146t) This can be programmed into a spreadsheet or a sci calculator. Unfortunately you need to make an equation for each film + dev combo, based on the published charts for the exponent AND your individual time at a known temperature for the multiplier (59.4 in my case). But I only used one film + one developer in those days. Hope this is helpful

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