Unexpected film testing results

[shannaford]

Had some unexpected results from film testing the other day, and just wondered if others had had similar experiences. I was testing 4x5 sheets of delta 100 in a 3006 expert drum with ID11 mixed 1:1. First step was to give it a five min presoak on the CPA at my normal rotation speed (setting 3, about 50-60 rpm).
According to Jobo, with a 5 min presoak times should come in around the same as for standard inversion developing, but here's the unexpected part. Ilford recommends around 11 mins for ID11 1:1. But my testing resulted instead of a time of 7min15sec. I then went on to test for N+1, N+2 etc and the test results seem to work out fine, I'm just wondering why my times would be so much shorter than expected by Jobo/Ilford? I did all my testing with a reliable densitometer, and temperature during developing was a constant 20 degrees C. Anyone else had similar experiences?
Thanks, appreciate your thoughts,
Scott

[Brian Ellis]

Local water can make a big difference in times. I remember attending a workshop at Anderson Ranch and we were told to process our film for a considerably shorter time than we did at home because of something having to do with their water. Also, Ilford used to recommend against presoaking their films. I wouldn't have thought presoaking would affect the times but if you feel like testing again you might try it without a presoak just to see what happens. I think presoaking is a waste of time anyhow, I never found a need to do it with today's films though I know people still do it and presumably they find it beneficial, I just never did.

[ic-racer]

If you prints look good then be happy!

If you want to track down the discrepancy, it could be many things like, the densitometer is 'reliable' but does it accurately read a 1.8 log d standard?
What gamma does Ilford get with 11 min. (do they say?). What gamma are you getting? Any errors in dilution? Jobo at 20c? Built in thermostat or external thermometer? Is temp. measurement accurate?

[shannaford]

If you prints look good then be happy!

If you want to track down the discrepancy, it could be many things like, the densitometer is 'reliable' but does it accurately read a 1.8 log d standard?
What gamma does Ilford get with 11 min. (do they say?). What gamma are you getting? Any errors in dilution? Jobo at 20c? Built in thermostat or external thermometer? Is temp. measurement accurate?

Yep, doing my best to keep the variables under control - external themometer used, distilled water, densitometer tested regularly against a known step wedge etc. As you say, if it works, great! I'm just curious, because I thought a presoak was designed to normalise the processing times somewhat, to make them closer to the standard times. Obviously rotary processing on its own can increase contrast etc and thus usually requires a reduction in processing times, but it appears this reduction is still required, even with the presoak. maybe as Brian suggests, the presoak is a waste of time!

[Richard Littlewood]

My times are shorter than that. I use ID-11 @1+2 with FP4, same methods, and get times between 10.5 and 12 mins.

[Joanna Carter]

Obviously rotary processing on its own can increase contrast etc and thus usually requires a reduction in processing times, but it appears this reduction is still required

The agitation from a Jobo seems to be very vigorous; I develop Acros in DD-X at 24° and found the only way to get negs that weren't soot and whitewash was to reduce the developer concentration from 1+4 to 1+9. This was more effective than reducing time, as the resultant shortened times ended up being so short that N- development could be less than 4mins.

maybe as Brian suggests, the presoak is a waste of time!

I live near enough to Ilford to "pop in for a chat" and, when I discussed using the Jobo processor for Delta 100, I was told to avoid the prewash as the emulsion contains a wetting agent (or something like that). When I mentioned the "normal" Jobo cycle included a prewash, they said, if I insisted, to reduce any prewash to as little as possible. In fact, even though the prewash didn't seem to make any difference, I haven't had any problems with negs developed without any prewash

[percepts]

Thats the whole point of testing. If you blindly follow what others say you can be miles off for your own kit and working procedures. If your results worry you, it is worthwhile repeating them to prove consistency for every development. And that consistency is what you are looking for. Any rotary processor will shorten dev times from normal. That's what constant agitation does. I think jobo said 15% shorter but 30% or so is perfectly acceptable, especially if you are developing to a lower contrast index than ilford use for ISO speed testing.

[hka]

My experiences are in the same matter. Dev-times aroud the 7:30 - 8:00 min. are not unusual.
50-60 Rpm's are to fast for a expert drum?
Jobo recommend a speed around the 25 rpm or slowest speed that's possible.
IDK if this wil work on the CPA's.
It's better for the motor and better for keeping the highlights under control.

[Kirk Keyes]

I live near enough to Ilford to "pop in for a chat" and, when I discussed using the Jobo processor for Delta 100, I was told to avoid the prewash as the emulsion contains a wetting agent (or something like that).

Once the film is wet, either from the prewash with the wetting agent from the film or from the developer with a wetting agent from the film, it's wet.

Use a prewash or not and determine a time for your system.

(I use a Jobo and I prewash, just for the record.)

[Joanna Carter]

(I use a Jobo and I prewash, just for the record.)

That's up to you. I'm just telling the official Ilford technical advice which is that it is strongly advised against for quality reasons, not just a case of you don't need to do it.