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So I'm wondering...as I sit here and process some 12x20 negs...about increasing or decreasing developer temperature.
I am curious about the temperature of the developer. Let's say you ran a batch of film at 70f and at 80f and compensated for time. Would the negatives have different contrast curves? If so...which would film would be higher or lower contrast?
I'm sure this has been beat to death, but I'm not sure I've read anything about it lately.
Thanks!
With a high degree of reliability for conventional developers over surprisingly wide temperature ranges a properly calibrated time-temperature chart will deliver consistent amounts of development "effort" with predictable density and contrast outcomes. I've found that the time-temperature charts (plotted: logarithmic time versus linear temperature) for all the conventional developers I've tested are parallel.
In my own darkroom I find sheet film developed in my replenished Xtol at 30 Celcius for 4 minutes looks the same as film developed at 20 Celcius developed for 11 minutes 15 seconds. This is useful because accurate temperature control is very difficult while accurate time control is very easy. I just measure the developer temperature and set the timer accordingly.
Informal testing suggests this approach is not so reliable with divided developers, staining developers, stand development, and monobaths but I no longer mess with that stuff anyway.
Hydroquinone becomes proportionally more active above 75F, and is a higher contrast developer component, so above that temperatures, developers with hydroquinone should tend to be contrastier. That behavior is used to kick contrast on papers, though I don't know why it wouldn't work equally with film.
More temp makes the dev more active, so obviously increases contrast; and yes, within reason you can time-compensate for this and achieve analogous curves, that is, close enough for general printing purposes. But anything above 75F often risks emulsion damage. But you'd have to plot your own specific fim/dev/time-temp curves if you want a precise answer. Different dev ingredients might behave differentially in relation to each other at nonstandard temps.
This is most easily detected in prints where you get a somewhat different image color at different temps even though you've compensated the time for overall
contrast.
Depends on the film/developer combination - some can show changes in curve shape when you change time/temp while holding overall CI constant.