Jobo Expert Drums: Reduce Time or Dilution?

[neil poulsen]

I develop sheet film (Ilford HP5) in D76 1:1. If I use a Jobo Expert drum, I understand that because of the continuous agitation, I need to reduce either the time of processing (in the developer) or the dilution of the developer.

Which is best, and by how much to obtain the same results as my dip-and dunk approach?

The Jobo site once had a description of this by John Sexton, but I can't find it now.

[Bruce Watson]

It depends. Different films/developers react differently. There's a short study by John Hicks published here:

http://unblinkingeye.com/Articles/Rotary/rotary.html

In my experience, you can only shorten time so much, then you have to increase dilution. I really wanted to use HC-110 (no, I don't know why ;-) with 4x5 Tri-X in a 3010 drum, but I couldn't get a dilution/time that I could live with. Even 5 minutes with dilution H was giving me too much contrast/density.

With constant agitation, the rule of thumb is that development time varies as the square root of dilution. For example, if your time is five minutes and you decide to triple dilution, your new time is (5)(sqrt(3)) or 8.7 minutes. It's a rule of thumb -- a starting point for testing, as John Hicks shows in his article.

Once you get it dialed in though, rotary processing with the expert drums is amazing. Utterly consistent, completely predictable, and completely even development. For me, it's the only way to develop film. Of course, YMMV.

[mark blackman]

for what it's worth, I found that there was no change in time or dilution required when moving from a Doran tank (15 seconds of inversion per minute) to a Jobo Expert tank. That's with FP4 and Ilford HC at 1:31, 7 mins at 20 centigrade.

[Gem Singer]

Hi Neil,

Ilford recommends reducing the development time about 10-15% when changing from slow intermittent agitation to continuous agitation. They classify tray development, as well as rotary development, as continuous agitation. No need to dilute the developer any further unless your developing time is under 5 minutes.

If you would like to try a different developer for HP-5+ film, I recommend Ilford's Ilfotec DD-X. It can be used at the standard dilution of 1+4, or it can be used at 1+7 or 1+9, with longer developing times. It's a little more expensive, but it is a liquid developer, with a relatively long shelf life, that was formulated to be used with HP-5+.

[Darin Cozine]

According to the Jobo site, most developers will not need a reduction in procesing times. The noted exeption was Xtol. Interestingly, they also mentioned that E-6 developers actually need more time in a rotary development.

I thought that Ilford reccomended 5-15% reduction in developer times, but I cant find that page now.

I also checked the massive developer chart at www.digitaltruth.com but there was no data for rotary development [with d-76 and hp5]

[Gary Frost]

I use HP5+ 5X7 in a Jobo 3006 with D76 1:1 at 68F ( 1000ml working for 6 sheets) My times are 8 min for N-1 and 9- 9'30" min for N. I rate it at full speed EI 400 and have no problem with shadow density. (using diffusion enlarger and Ilford MG IV @ Grade 2) ...just for a point of reference....YMMV

[tim atherton]

"According to the Jobo site, most developers will not need a reduction in procesing times. The noted exeption was Xtol. Interestingly, they also mentioned that E-6 developers actually need more time in a rotary development."

The reason for that is that Jobo found that a 5 minute presoak "levels the playing field" for most films, so you can take the non-contstant agitation time, use a 5min presoak and keep the same time.

The reason Xtol is different is that Kodak ran extensive development test for Xtol including times for continuous agitation - so you use the Xtol times for cont. agit. but with no pre-soak. If you use a presoak it then messes up the times Kodak arrived at.

[Gary Frost]

Forgot to mention and Tim reminded me: Regarding the above times, I use a 5 minute presoak on all films.

[Tom Westbrook]

Neil, Jobo's article by John Sexton you were looking for can be found here:
http://www.jobo-usa.com/jq/jq9403.htm#UPJS.

For dilutions, I usually use 50ml of stock solution per sheet of film, which is what Jobo recommends (http://www.jobo-usa.com/instructions/instructions_misc_expert_drums.htm). So for D76 1:1, you'd need 100ml/sheet, with a max of 1 liter for a full 3010 drum with 10 sheets. Seems to work OK for me.

[Don Wallace]

I develop HP5 and Tri-X in a Jobo (not Expert drum) and found that the development times were a little shorter than with trays. Mind you, continuous tray agitation is a LOT shorter than tanks. I use HC-110 and found that I had to go to dilution D, E, and F, to get the times I wanted (N, N+, N-).