Is the Ilford temperature conversion chart reliable?

I was just wondering, are there people who use the temperature/time

conversion chart available on Ilford's website with various films and

developers? Is it just to be used as a general guide that can have

slight variations with films and developers, or is it completely

reliable with any combination? Thanks.

It has worked for me with all of the (limited) combinations I have tried. Your mileage may vary of course.

It is reliable, but i don't encourage my students to find the need to use it. Maintain consistency with the same temperature is the order of the day in our classes.

 

However, at times people are not paying attention and then we need to use that chart. Just happened yesterday with someone who just returned from some time off and they just zoned out. So , we had to make a correction 4 minutes into the process.

Oliver

 

I lived in the tropics for years and the water was always more than 28 deg.C., so I used the table most of the time with good results. As noted, tests are the best way to determine the times/temps that work for you.

 

Cheers

I use mostly Ilford products in my darkroom, but I often wonder about their scientists. While Kodak's product sheets are accurate, Ilford's should only be taken as a general guide. What I do is empirically calculate the percentage decrement in development time per degree of increase in temperature and apply that anytime I use a higher temperature. For instance, I note ID-11 requires a 3.3% decrease in development time for each degree Fahrenheit above 68 degrees. Hope this helps.

I've found Ilford's data for film development and print exposure using their products to be accurate enough that I need to make only minor adjustments from their baseline to suit my preferences. I began using Ilford products for the first time only three years ago and found that making the adjustment from Kodak materials to be quite easy.

 

There are a very few exceptions. Many of us who enjoy using Delta 3200 find it works best with more development than Ilford suggests. So if I'm exposing it at 1600 I'll develop as for 3200. When exposing at 3200 I'll develop at least 25% longer to enhance contrast. (Delta 3200 is a low to moderate contrast film).

Thanks so far. The question occured to me because near the chart the text says that it is correct for all film/developer combinations, but as I have read, different developing agents react differently to change of temperature. Is that difference so little that in practice it does not matter?

I have used those tables for D76 1:0 and when I used distilled water for HC110. I don't want to store anything in our fridge because we have small children. It was a hot summer and everying was around 24degC in my darkroom so I used the charts to get the right times and all worked well but you really should pick a temperature and try to stick with it and adjust from there. I would say that developers may work differently at higher temperatures but to be sure you would have to test them at different temperatures and compare the results.

The tables are based on the combination of ID-11 and FP3 (!). They work quite well with ID-11 and any film; and also work quite well with some other developers, including I think HC110. But some modern developers such as XTol, TMax, or ILFOTEC DD-X do not show the same change in activity with a change in temperature; if you use the chart for these developers, you'll likely end up with underdeveloped negs at higher temperatures.

In the last few years, an attempt was made to move away from the charts, and testing was conducted at both 68? and 75? on new films, but the resources were not available to fully test all films at both temperatures. If you are using Delta 400 or 3200, use the times listed in the box; for intermediate temperatures, you can get a pretty good time by extrapolating in a straight line; the variation isn't enough to mess up anything short of scientific work.

 

If you're using a modern developer and other films, do a little testing. IIRC, for these developers, the chart showed about an extra 50% change over what was really required; so if it calls for 30% less time, test at 20% (but do a test; I'm working from memory here).

 

Best bet of course is to work at 68?, but that's a lot easier for someone in New Jersey than it is for someone in Florida. ;-)

 

 

David Carper

OK, sorry about bringing this one back, but the question came up somewhere else, and I needed something to point to.

 

This one comes up in a Google search.

 

Development is Arrhenius, and so the Arrhenius equation can be used to find the times

for different temperatures. It seems that the activation energy needed is close enough to

constant that Ilford publishes graphs and tables that are independent of the developer used,

at least for small temperature differences, and likely for not so small ones.

 

See:

 

Arrhenius equation - Wikipedia

I am using Ilfosol 3 here in Phoenix AZ (USA), where only during the last week or two have the daily high temps dropped below 100F (38C). Because there's no practical way of holding chemistry temps at 68F (the water temp runs about 75F here during the summer), I simplify my temp control by using bottled (either distilled or RO) water in gallon jugs, then hold it indoors in my apartment where the temp is pretty much 72 +/- 1 F. The Ilford chart tells me I need about a 15% reduction in time from 68F/20C, and based on developing about 50 rolls so far (a mix of Ilford, Tmax and Arista), it looks spot on as far as I'm concerned. FWIW, I'm processing my B&W film in a 50-year-old half-gallon sized (8 rolls of 135, 4 of 120) stainless steel Honeywell Nikor tank. Nice dense negs (I usually overexpose by about 1/2 stop), I'm pretty happy with my results.