Rotary Processors - time adjustment??

[Matthew Rolfe]

I am using a Jobo 4531 tube on a Jobo rotary base to process 10x8 b&w film but am not sure about the time adjustment - if any - I should make when using a rotary processor? Digital Truth state on their massive dev chart that a time reduction of 15% should be made when using a rotary processor, or rather it is advisable......

Firstly, I have two speeds of rotation on my Jobo base, so I'm not too sure which the 15% time reduction is applicable to? I would imagine the slower of the two but could someone confirm? Secondly, will developer (in my case Rodinal) exhaust much more easily over a longer period of time? If so, should I be diluting at 1:25 so that the process is shorter?

Many Thanks

Matthew

[venchka]

I use a 3010 on a Bseler base for 4x5. Xtol 1:3. 30-32 RPM. 10 minutes is spot on for HP5+ @ 250 and very close to spot on for everything else. Kodak's time is 10.5 minutes for HP5+ @ 200.

Personal testing will tell for sure.

I subtracted 20% from Ilford's time for D-76 1:1.

[Nathan Potter]

I come up with approximately 20% time reduction with a reciprocating Unicolor drum system over my dip and dunk times - everything else being equal. But you should run through a full calibration sequence for a particular film as a function of how you print with a particular paper.

Nate Potter, Boston MA.

[Peter De Smidt]

For most developers, Jobo USA used to recommend a 5 minutes pre-soak with tempered water. They found that if you do this, you could then develop for the recommended times for inversion processing and be very close to correct. They were not able to find a single % reduction from inversion times that gave the correct times for rotary processing.

Xtol was the exception, because Kodak had gone to the trouble to give rotary times for it.

The only purpose of the pre-wash, according to Jobo, was to help determine development times.

[venchka]

For most developers, Jobo USA used to recommend a 5 minutes pre-soak with tempered water. They found that if you do this, you could then develop for the recommended times for inversion processing and be very close to correct. They were not able to find a single % reduction from inversion times that gave the correct times for rotary processing.

Xtol was the exception, because Kodak had gone to the trouble to give rotary times for it.

The only purpose of the pre-wash, according to Jobo, was to help determine development times.

Regardless of how all of this came about, I do in fact pre-rinse all my film for 5 minutes. I follow the Xtol 1:3 rotary times from an old Kodak German tech bulletin for Xtol. I start with the Kodak times and adjust slightly for personal taste.

[Jehu]

This web application helped me:
http://www.phototec.de/e_rechner.htm

I don't speak the language but, fortunately, you don't really need to. I use it every time.

[Matthew Rolfe]

Thankyou for all your advice!

[Peter De Smidt]

Hey Jehu,

Thanks for the link. That's pretty cool!