Did you mean this"(posted 8531 days ago)"I never claimed to be the cripiest fry in the basket, but I could NEVER understand why Ilford instructions packaged with developer and tech sheets have the same goofy TIME/TEMP conversion chart/graph.
Blamed thing is useless IMHO - too small and vague - leaves you guessing. Why can't they just publish T&T like Kodak does in their B&W Darkroom Dataguide - i.e. Tri-X Pro at iso 320 in D-76 1:1 @ 65 68 70 72 & 75 degrees or whatever?
Then I came across a conversion method in Aaron Sussmans book from the late 60's "Amatuer Photographers Handbook".
You take the given time at ANY given temperature for whatever combination you've got and can calculate the given time at any other given temperature fairly quickly and certainly with a finer degree of precision than with the aformentioned graph.
I know this may seem hypocritcal coming from a guy who develops by inspection and "eyeballs" exposures with an incident meter but I find it re-assuring to have something that seems at least a bit less of a SWAG than the chart.
It goes like this:
"Given the developing time at 68 degrees, you convert to the time at any other temperature by multiplying the given time by the desired temperature factor T. To convert from the time at any temperature other than 68 degrees, to any other temperature, you divide the time of the given temperature by its own factor and then multiply by the factor of the desired temperature."
Here's the chart:
Temp in Farenheit followed by factor
64 deg factor 1.23 65 1.16 66 1.10 67 1.05 68 1.00 69 .95 70 .90 71 .85 72 .81 73 .78 74 .75 75 .72 76 .69 77 .66
This is on page 382 of the edition I have. Hopefully the times and factors will line up when I "send" this to the forum. FWIW Sussman has all kinds of neat info in his book. It would definatley behoove us to look over old photo manuals at yardsales, library used book sales, etc. etc. etc. My copy came with an enlarger my wife bought me a while back."