Jobo agitation and reduction in development times

[612tom]

Hi

I have the smallest of the Jobo tanks that fits 4x5” sheet films, a 2500 tank.

I currently rotate it by hand with constant agitation when developing. I've tried floating it in a sink of water to make the rotation easier, but the tank floats too low in the water and water pours into the tank through the filling spout (I don’t have a lid/cap for the tank) and dilutes my chemicals

So I’ve been looking at getting the Jobo manual roller base for the tank, to make agitation easier. Does anyone have one of these? I’m concerned that the rollers might be spread too far apart (width-ways) to cope with the smallest of the Jobo tanks like my 2500, which is barely over 4 inches wide. Same story with the used Beseler or Unicolour motorised roller bases that you might be able to find on fleabay – are the rollers too far apart for a small tank like mine?


Secondly – when using constant agitation in tanks, one reduces the development time by 10 or 15% according to the dev’s instructions. I’m using Delta 100 in Ilfosol 3 for 5 mins, less 15% = 4 minutes 15 seconds. However my negs still are really contrasty and over developed. It’s possible my dev was a little warm (tap water came out at 25degrees – it is Summer here after all!) but I think I need to further reduce time for constant agitation. Does anyone have any pointers??



Thanks in advance

[ic-racer]

Sure, it is trial-and-error. Even if you are using a sensitometer to make film curves. Go colder or use a shorter time. A pre-wash can also slow development to some extent.

Don't just guess, though. Print those negatives and see if they are really too contrasty.

[Richard M. Coda]

What dilution? You may want to either use an ice bath to cool the water down or try a more dilute developer.

[jeroldharter]

The manual Jobo roller base is adjustable to accommodate the various sizes of Jobo drums including the 2500 series and the expert drums.

[612tom]

Sure, it is trial-and-error. Even if you are using a sensitometer to make film curves. Go colder or use a shorter time. A pre-wash can also slow development to some extent.

Don't just guess, though. Print those negatives and see if they are really too contrasty.

Pre-washing with Delta 100 isnt recommended I think, and I have scanned / contacted printed the negs - the contacts are really blocky, although the Scans do have detail in the blacks if I fiddle...

I guess you can always add contrast when printing or photoshopping if you wish, but reducing contrast or regaining details lost to the blacks and whites is more of an issue.

What dilution? You may want to either use an ice bath to cool the water down or try a more dilute developer.

1+9 for 5 mins, although there are timings for 1+14 for 7.5 mins, so maybe I should try a more dilute solution like you say. I just went for the normal 1+9 as it was only a 5 min development time and I didnt want to stand there hand turning the drum constantly for too long!

The manual Jobo roller base is adjustable to accommodate the various sizes of Jobo drums including the 2500 series and the expert drums.

Ok great, maybe I'll have a look for one of these. Or a motored base of some sort.


Cheers

[Lachlan 717]

Couple of things:

First, there is a basic Jobo processor on Aussie eBay at the moment. Might be worth the investment;

Second, if that's not an option, don't bother with a Jobo roller. Just get a shitty old skate board, cut of the trucks/wheels and make a roller out of them. Easy and cheap.

[612tom]

Couple of things:

First, there is a basic Jobo processor on Aussie eBay at the moment. Might be worth the investment;

Well found my friend

These dont crop up used on our shores often do they!


Cheers

[Lachlan 717]

Well found my friend

These dont crop up used on our shores often do they!


Cheers

Not down here!

I got one a couple of months ago (with the tilt
arm, though) for mid $300s, pick up.

Now just got to stay in the country long enough!

[venchka]

Pre-washing with Delta 100 isnt recommended I think, and I have scanned / contacted printed the negs - the contacts are really blocky, although the Scans do have detail in the blacks if I fiddle...

Cheers

I see that a lot on the Internet. Don't pre-wash. It's a good thing I can't read.

Maybe it's Delta 100. I have much better results with Arista.EDU 200, Efke 25, Tmax 400, etc.

[Bjorn Nilsson]

If you intend to stick to the current dilution (and the consequent short development time), I would definitely consider pre-washing. In my experience, pre-wash "evens out" any differensies in how and when the developer starts to work on the different areas of the film. I've pre-washed just about every film I've processed for the last 20 years and I've never had an issue which could be traced back to the pre-wash. If in doubt, try it with some shots which you can live without if the processing should mess up for whatever reason. Anyhow, add some 20 seconds to the dev-time after pre-wash to compensate for the time it takes for the developer to replace the water in the emulsion.
Constant agitation is different in different tanks/drums. So, constant agitation with a CombiPlan is not the same as rotating a Jobo (where the 2500 and the Expert drums differ as well.) With some combinations, you don't have to compensate at all, while others require up to -20% reduction in time. You have to conduct your own tests.
I just had a brief look into my darkroom/processing room, where the thermometer reads 14 degC. I definitely don't have any problems with over-heated developer this time of the year.

//Björn