Development time versus temperature - how accurate chart is?
Sometimes I have really problems to keep my water bath at desired temperature.
So it would be lot easier to use current room temperature. But that raises a question.
How accurate are temperature/developing time conversion charts - I use Ilford's chart as an example because it is well known (http://www.digitaltruth.com/devchart.html ).
For example, if I have calibrated my developing times for temperature of 24°C, can I trust that result is almost identical at 20°C if I just adjust development time using chart?
Is there any test lying on the net?
I use the Ilford chart and in summer time I process at 24 C as that is about the coolest I can get the water down to without too much hassle.
In winter I switch to 20 C and once again I use the Ilford chart as a guide and find it accurate.
Strictly speaking you should only use one temperature, but in reality there has to be a bit of leeway.
I process Tmax 100, FP4+, HP5+, Neopan 400 and recently some Panatomic X, using D76 @ 1+1 . I find no discernable difference when I switch between temperature and time variations.
But on that note, if you pick a temp, stick to the time on the chart. Straying too far might affect development.
It's never too early to panic.
Traditional Blowhard Extraordinaire
Please keep in mind that ALL CHARTS are suggested starting points and not cast in concrete. Film development times, unless otherwise stated, are for 35mm film, manually developed. Film and paper emulsions do change with batch and age.