About developing two 35mm films in a Jobo tank

Greetings! Here I am again trying to tap into the expert knowledge of the members of this forum.

Here's the situation: I've been using a Jobo tank with 500 ml capacity to develop my films (Agfa APX 100) one at a time. I've been developing them in Rodinal 1+50, that is, 10 ml Rodinal in 490 ml of water for 17 minutes at 20°.

My question is: Can I add another film to the tank and safely develop two films without changing anything else? Or will this amount of developer not be enough for two films?

I'll be very grateful for your help.

Ed

There was a discussion a while ago about minimum amounts of Rodinal that can be used, some places say 10ml/film, some 5ml, and despite that there are people who still have perfectly good results at 1ml/roll. As usual, it really depends on how and what you've shot, if it's a lot of dark or a lot of light, and whether you're picky or skilled enough to be able to tell the difference if there wasn't enough in there...
Personally, I'd have no problem with it, 5ml is fine for me, but others will probably disagree.

edit: maybe there has been more than one thread...
(there was a url link here which no longer exists)
(there was a url link here which no longer exists)
(there was a url link here which no longer exists)
etc

Yes, with Rodinal 1+50 no problem for sure. I use 7ml for 2 rolls (Rodinal and APH09, 1+100) - no problems at all.

There are many threads and opinions on this. To summarise:
- Agfa says 10mL/roll is the minimum, and that minimum was probably computed conservatively on the basis of a heavily-exposed (high key) roll
- some people report it's OK with 5mL/roll, but they don't seem to have run scientific comparisons
- if your rolls are lightly exposed (low key), the smaller amount of concentrate is probably totally fine

Try it for yourself, but be serious about it: don't just stick two rolls in and go "oh yes, I still have images" - of course you will get SOMETHING. Expose three rolls (A, B, C) where A and B are identically exposed. Develop A on its own, then B and C together. Compare A and B. Be absolutely rigorous in your time, temperature and agitation control or the results will be meaningless. If you're not rigorous in your development process-control anyway, then probably you won't notice or care about any quality loss from over-exhausting the developer.

I suspect that you will observe some density loss if the rolls are heavily exposed, but that this could be compensated by extending the development a tiny bit when there are more rolls present. At least, that is the documented (by Kodak) behaviour of D76 when you use slightly-insufficient stock (150mL instead of 250mL). I would find that painful though, because it means your results (film speed, contrast, etc) are not repeatable because they depend on how much the roll (and the other roll in the tank!) was exposed. You want your development to be a fixed, known thing that will achieve a specific result from your film, and knowable before you push the button.

Hi. I see no problem with this. The only problem I had with Rodinal in a Jobo tank was with minimal agitation. Faint unevenness or similar to surge marks. I cured this by using only one film at a time and loading an empty spiral in the bottom as well. If you use "Normal" agitation then two films will be fine.

Edimilson said:

Greetings! Here I am again trying to tap into the expert knowledge of the members of this forum.

...

my films (Agfa APX 100) one at a time. I've been developing them in Rodinal 1+50, that is, 10 ml Rodinal in 490 ml of water for 17 minutes at 20°.

Click to expand...

That is 1+49.

I use 15 mls in 1500 mls for 5 x 36 films ie 1+100 full stand no agitation for 60 mins at 20C Patterson multi.

Not detected any compression though normally get blown high lights with silver rich film. Shoot APX100 at box and APX400S at 320 another 1/3 of a stop off each may be better for wet printing.

1+50 may have a different rule set, but 10mls for 2 films should be ok IMO.

1+100 is more economical but you get flat negs.

If you always need to do two 135s at once then the 1520 tank with two reels which is what I assume you have, is fine but if you need to regularly do one 135 film it might be worth buying a 1510. This only needs 25Omls and over time the saving in developer and fixer will pay for the tank.

pentaxuser

My first photography teacher and mentor used to develop Agfa APX25 35mm film in Rodinal 1+300 in normal size tanks. Less than 1ml per roll. He made 40x60" prints from those negatives and got spectacular results. Imagine an enlarger head all the way to the ceiling, and paper on the floor kind of thing.

Anything is possible. Try it for yourself and see if your results are acceptable or not.

If you use Rodinal a lot, you will learn that it's an extremely powerful developer that keeps on developing and developing and developing. It is slow working, so if you use high dilution you will need very long developing times to get the same contrast. If you agitate normally you will get a pretty straight line tone curve. If you slow down agitation the same film will shoulder off while your mid-tones get more contrast - perfect for portraits.
Some films work better for this than others. The last version of the old Agfa APX 400 was hopeless in that you got to a certain point of developing and gamma would not increase no matter how long you develop. Films that work really well with Rodinal, in terms of shaping the tone curve are: FP4, TMax 400, APX 100, Tri-X 400.

Wow, there's lots of information to consider here. Thanks a lot! I am inclined to give it a try, but I'll go through all your contributions once more before making up my mind. Thanks again!

pentaxuser said:

If you always need to do two 135s at once then the 1520 tank with two reels which is what I assume you have, is fine but if you need to regularly do one 135 film it might be worth buying a 1510. This only needs 25Omls and over time the saving in developer and fixer will pay for the tank.

Click to expand...

The OP has the opposite problem: not enough room in the tank due to using high dilutions.

polyglot said:

The OP has the opposite problem: not enough room in the tank due to using high dilutions.

Click to expand...

I suppose I was making the assumption, perhaps unwarranted, that 1+100 or even Rodinal per se wasn't necessarily the "holy grail" but that's what he had to use. If Rodinal 1+100 is the sine qua non then of course he has no choice but to use the bigger tank. Only 2.5mls of Rodinal certainly might be "pushing it"

I was looking ahead to the day when he decided that there were other good developers to try when the smaller tank has advantages. He might then have thought of this change of tank himself without my help. It's always difficult to know how much ,possibly extraneous, advice to offer

pentaxuser