Mixed film sizes developing capacities of chemicals

[Jim C.]

I'm about to have a go at developing C-41 after the good results I got from trying my hand at E-6
I want to try a mixed film format developing run, 4X5's and 120, in a 2553 tank with reels in a CPA2
and I want to double check my math with those that might have done such a developing run.

The Jobo C-41 press kit has a chart for the amount of developer needed for X number of sheets
or rolls, I'm guessing that it's based on square inches of film that needs to be developed.

So, as a starting point, 240ml will develop 2 - 120 rolls which is 162.5 sq.in.
(120 roll = 81.25 sq.in. )
the same 240ml will develop 8 sheets of 4X5
( 1- 4X5 sheet = 20 sq.in., so 8 sheets = 160 sq.in. )

Am I correct in assuming that as long as I make sure that the combined sq. inches of film, 4x5 and 120,
equals 160 - 162.5 sq.in. for 240 ml of chemicals I should be copacetic ?

[Mick Fagan]

Jim, pretty much you are correct in that square area of sensitive material that has to be developed, is related to the amount of developer. In the case of colour developers, that figure is of course, undiluted.

Using one shot C41, 1 litre of developer is correct for 8 rolls of 135 film. Or, to put it another way, that is 8 sheets of 8x10" film.

I can vaguely remember reading when I first got my Durst Printo paper processor, that there was a general consensus among chemical suppliers/manufacturers that 1 litre of chemicals, should do 1 square metre of sensitive material.

I worked out this 1 litre per 8 rolls of 135 film thing, about 21 years ago when I first bought my CPE2, been using it ever since, although I now mix my own C41, have done for about the last 15/16 years.

But what is, "copacetic"? At first I thought you were referring to acetic acid, but now I don't think so.

Mick.

[Nick_3536]

The rule of thumb is one 35mm 36 frame equals one 8x10. Kodak actually publishes the square inches for the different formats and even includes figures for formats without perforations. Which I guess could add up on a big processor.

Memory tells me a roll of 120 is slightly less then a roll of 35mm/8x10. Check the Kodak website. Info should be in the C-41 doucuments. Z-119?? Or maybe Z-131

[Don Hutton]

Using one shot C41, 1 litre of developer is correct for 8 rolls of 135 film. Or, to put it another way, that is 8 sheets of 8x10" film.

Those figures are at odds with the figures Kodak supplies in their Z131 manual which states 3 8x10s per liter or 4 rolls of 36 exp 135mm. Capacity of other solutions is double the developer capacity... see Table 3-3 here http://www.kodak.com/global/plugins/...ls/z131_03.pdf

Am I correct in assuming that as long as I make sure that the combined sq. inches of film, 4x5 and 120,
equals 160 - 162.5 sq.in. for 240 ml of chemicals I should be copacetic ?

I mix formats all the time - no problems at all having different films formats on different reels in the same tank.

Yes - no problem here with the numbers, but be aware, there are some specific instructions for the press kit relating to capacity or different speed films - basically, you will get more capacity with slower films. Also, using the press kit on a rotary processor, you are advised to use the solutions "one-shot" only due to the oxidation effects caused by rotary processing - so make sure your solution volumes are based on "one-shot" use.

Also, make sure that you use at least the minimum chemistry volume as suggested by Jobo for the particular drum - in that drum I would not never use under 640mm unless I was only processing two rolls of 120 - on separate reels loaded on the outside only.

I've never used the press kit although I keep it in my darkroom for emergencies. The regular Kodak C-41 chemicals are reasonably inexpensive and give great results.

[Jim C.]

Thanks for all the replies !
I'll look into the Kodak info but for now I want to use up the Jobo press kit I have
before I go and buy a Kodak C41 chemical kit.

But what is, "copacetic"? At first I thought you were referring to acetic acid, but now I don't think so.

copacetic is just a old word I picked up eons ago, it means in excellent order

Also, make sure that you use at least the minimum chemistry volume as suggested by Jobo for the particular drum - in that drum I would not never use under 640mm unless I was only processing two rolls of 120 - on separate reels loaded on the outside only.

I try to mix 1000ml of chemicals and divide that up into the recommended solution
amounts between the 3 different Jobo tanks I have so that I can use up all the mixed
chemicals as soon as possible depending on what the format quantity is that I've shot.

I'm not sure what you mean by the 120 film loaded on the outside.
The 2502 reels can hold 2 rolls of 120, do you mean a single roll of 120 per reel ?

[Don Hutton]

I'm not sure what you mean by the 120 film loaded on the outside.
The 2502 reels can hold 2 rolls of 120, do you mean a single roll of 120 per reel ?

Yes - the 2500 reels can hold 2 rolls of 120 - one on the outside, one on the inside (i.e. if you're loading two, the roll which is passed the red clip, I am referring to as the "inside" roll, and the roll loaded second I am referring to as the "outside roll" - outside of the red clip). Some of the tank minimum capacities given by Jobo refer to single rolls of 120 loaded on the outside. For example with your 2553 drum, you could in theory process three rolls of 120 in that drum in 330mm of solution at the same time, if they were loaded onto three separate reels and all three rolls were loaded in the "outside" position on each reel. If you loaded 2 rolls onto one reel and one onto another reel in the same drum, you'd need at least 640ml to ensure that the "inner" roll on the first reel was covered with chemistry during rotation.

Be careful with using Jobo's recommended minimums - they work, but they require careful set-up - the drum in position must be perfectly level to get away safely with those recommended minimums. In practice, I generally use a bit more.

[Mick Fagan]

Don, very good points there! I checked out the link, yes it is at odds with some Kodak literature that I have, although my Kodak stuff is dated. My C41 processing manual is 1975 and the supplement for rotary processing is dated Nov 1975. I have been using them for quite some years now.

The only real way to determine if you are correctly developing C41 (all colour AFAIK) is to use control strips. The last time I used control strips was some time after 1991, although a friend who is a retired chemist and recently took up developing his own C41 used my home brew C41 developer with control strips that were delivered in dry ice and kept in the freezer, things were still spot on, that was about 1½ years ago.

In earlier years, around the late eighties, both Agfa and Kodak were selling C41 kits in ½ litre sizes for the hobbyist, their stated capacity was 4 rolls of 135 36 frame C41. Tetenal at the time, IIRC, had a kit, that was good for 6 rolls of 135 36 frame C41.

So it appears that there was either a difference in quality aspirations of the amateur, or the professional films were treated differently, or possibly there were more active ingredients, or maybe they just didn’t worry about the safety margin for the amateur kits.

I have been developing C41 by rotary processing in my CPE2 since the late eighties, using the same C41 developer from the same batch of chemicals, just adding water. In that time I have run some huge batches of Vericolor II both S & L versions, many sheets of Kodak 4x5 internegative film for making accurate colour prints from transparency film. The internegative film is one film, which really does (did) require very accurate processing as it is intended that the end result is a technically pure and/or perfect colour print for display or reproduction purposes.

With all of these slightly differing process requirements and the fact that at the time Kodak did not offer one shot developer usage tables, I was forced to use control strips. Fortunately I had access (at the time) to a very well equipped colour lab. I duly processed control strips, had them read and plotted, then adjusted, if required. My notes from the last time I changed the set-up I had, dated in October 1989, tell me that at 12 rolls of 135 36 frame C41 per litre, things were not correct, just. At 10 rolls of 135 36 frame C41 per litre, I was within the guidelines by a reasonable margin. At 8 rolls of 135 36 frame C41 per litre I was bang on the money.

I did simulated tests to arrive at a close approximation of actual working conditions. Which means I developed 2 rolls of 135 36 frame C41 in the 1520 tank with differing amounts of developer, to get close, or to hone in. I then did working condition tests with the actual tanks and reels I intended to use. These were the 1500 series of tanks using three format arrangements. I used the 2 reel, 4 reel and 5 reel combinations of the system, as these were the expected processing sizes I intended to use. I also tested using a single 2509 reel in the base, or test drum, of the 2840 print film tank. Which in another brochure is a single reel 4x5 processing drum and the appropriate sticker on the outside. All of my full dress rehearsal tests worked perfectly and somewhere in my neg sheets of 1989 are all of the test films and the start of processing hundreds of C41 rolls and sheets per year.

So, with my basically empirical methods, backed up with some control strip data I do believe that there is (was) a big enough safety margin to safely say that 8 rolls of 135 36 frame C41 is (was) more than likely correct in 1989. It is quite possible things have changed so much in both developer and subsequent processing steps since my 1975 publications, as well as my 1989 tests, that my figures are relatively meaningless these days. This is something for me to ponder over, but I won’t worry too much as my system still works perfectly well for me. At least 1½ years ago the process was working very well, as that was the last time it was tested.

Jim, as noted by Don, watch those minimum amounts, it can be quite frustrating to have a perfectly developed half of a frame, personal experience here

Mick.