Gast
Hi there,
I’m assuming that the yields quoted by the developers’ manufacturers are based on 135 or 120 film. That’s always worked for me.
My question is: how many 4x5" or 13x18 cm sheets are equivalent to one roll of film??? Or rather, how many can I develop, for example, with a small bottle of Neofin Blaue?
By the way, how much Rodinal is needed for how much film??? Since large-format material is always best processed in plenty of liquid, and a 1:100 dilution isn’t bad in terms of contrast either, you start to have your doubts: 10ml makes a litre, so that would fit up to 24 4x5 films, for example (4 Jobo tins full, each 1/4 litre), but at some point it becomes homeopathic, doesn’t it?
Many thanks in advance
Martin
Gast
Well, Martin,
you’ve raised a problem that, once again, can only be solved by trial and error.
Converting a 135 film into square metres of exposure area is actually quite simple (your first question): 0.032832 square metres of exposure area.
A 9x12 cm negative has an area of 0.0108 square metres ((9x12)/10,000), so around a third of a 35mm film.
But if you perform heavy dilution of the Rodinal and thus create a lot of liquid, the ratio of developing agent to area to be developed will quickly become insufficient. You certainly won’t be able to get 24 sheets of 4x5” to come out black with that.
With 10ml of active substance, the developer will start to fail somewhere after the fifth sheet, and all five or more films will be ruined.
I would never develop more than five sheets at a time, except in undiluted stock solution A49 or D76. The risk of ruining all your shots is completely out of proportion to the 2 cents for the R09 (= Rodinal). Besides, you can’t control the contrast precisely that way.
Neofin Blaue is, of course, an expensive business. It might be worth sacrificing a few sheets of test sheet film to test your tank with your favourite dilution.
It’s best to use films that are really black so you’re on the safe side. Process them one by one for the same duration and measure on the densitometer to see at what point the first sheet no longer achieves maximum black.
But please don’t forget to test the extension factor beforehand if you’re going to have 10 sheets in the tank at once later on!!
Regards
Mirko
www.fotoimpex.de
Gast
Hi Mirko,
Did you really have to use 5 sheets? All the tanks I know use 6 ;-).
I’ve tried putting 10 ml of Rodinal into a 2500 ml Jobo tank. That works at a dilution of 1:50 or 1:100. But it’s good to know that 5 ml at 1:50 or 1:100 probably isn’t worth the effort.
The Amido one (no idea what the company’s called – you’ve got them too, square, with the films standing upright) works at 1:100, needs a litre and can’t rotate.
I’d roughly estimated 4x5 to be 1/4 of 120 (my 6x9 takes 8 shots), so that’s pretty close. Your calculation confirms my fear that with Neofin, I’d only be able to process one canister (6 films) per bottle.
It gets interesting with 13x18 in the little darkroom, because nothing rotates, and the volume-to-film ratio is absolutely dreadful. That would have to be 234/10,000 m, so about 1.5–2 sheets per film.
I’m so glad an 8x10 back is too expensive for me. That would only work in trays, one at a time, so it really does take a long time.
Gast
P.S.
Has anyone tried dilution of Neofin more than recommended? For example, using 1 litre from the bottle?
