Jobo ATL + Reduction of Developing Time
I've read various posts that suggest reducing the developing time by 15-20% when using a Jobo ATL1500 (and similar machines with constant agitation) when compared to manual processing.
I would think it has validity because of the constant agitation. I would like to get some thoughts from those of you who actually have had some experience with this.
Yes, it's because of the constant agitation. The 15-20% reduction will get you in the correct ballpark, but run some tests first. The tests will also give you an opportunity to get to know the processor better.
Also, remember that most development times are given for 68 or 70 deg F and the ATL1500 runs on 75 deg F only (for B & W). I.e. there is a big difference there too.
Last, if you want to process color (E6 or C41 at 100 deg F) the times given are usually correct.
I've been using my ATL1000 for a year and I'm very happy with it. It's really nice to just dial in the program, press a button and go for a coffee or whatever.
This is the first time I have mentioned this on this forum, but generally speaking when using a rotary processing system, you almost always, effectively dilute the developer, compared to conventional developing!
The reason is simple, if you use the Jobo 1520 tank you can develop two rolls of 135 or 120 films. Conventionally you would use 500ml of solution, however for rotary development, you will only use 250ml of solution.
This does have an effect. I bought my Jobo CPE2 in 1988 and I've processed just about anything possible to develop in it. I last used it on the weekend and will use it this weekend; it has had constant use since it was bought.
One of the first things I did was to see if there was much difference between constant rotary agitation and normal inversion agitation by hand. There is, but by my reckoning, not too much.
With colour processing, especially colour neg processing (C41) there is no dilution of the developer and there is no time difference for rotary developing. At the time I was working in a very big commercial colour lab/studio complex. I had access to Kodak C41 test strips and I had someone who could take careful readings using state of the art densitometry equipment. Best of all though, was the fact I could check the filmstrips I processed, with our pair of deep tank C41 processors.
Well there was a difference with my test strips, which is as it should be as I was using fresh chemicals and one shot processing whereas our C41 baths were huge replenishment systems.
The differences were minimal, and I mean minimal. The most important part, colour, was virtually identical. Not quite the same but realistically no difference.
Density was intriguing to the lab technicians; it turned out I was getting more consistent results than the lab. This was due mainly to fresh chemicals for every run.
The deep tank processors would sometimes sit around for 1 or 2 hours then all of a sudden start processing 100 to 300 4x5" sheets as well as about 200 rolls of 120 and the occasional 8x10" sheet, then nothing again until late afternoon when the shooting after lunch would come in.
After in-depth discussions with the Kodak technicians the lab actually bought a Jobo Autolab for processing of special E6 film. This was used in preference to our deep tank E6 processor as it gave more consistent results, especially for density where we would push or pull a 1/3 of a stop. This was only used for special shoots where colour fidelity and density had to be absolutely perfect. The E6 deep tank processor had the same quality issues of the C41 with no film for a few hours then bucket loads. The replenishment systems were always trying to catch up.
The upshot of all of this fiddling was that rotary development gave virtually no different results from a technical point of view with colour.
This made me think about B&W possible differences. So we started a developing test situation using Kodak test strips. We used the lab's roller transport developing (R/T) machine. Which if I remember was a 31cm Colenta E6 machine modified for B&W. The E6 machine was used as it could do a push or pull, which was beneficial for the different B&W times sometimes required in the first bath.
All B&W tests were done with Kodak TMax 100. The reason was that we were a Kodak lab and everything was Kodak.
Test strips done in a corrected bath for the B&W R/T machine each morning after the bath had stabilised.
I then did test strips at home using both inversion and rotary. The common denominator for these tests was that in all cases, the time the film was in the developer was identical. I cannot remember off hand what the time was but if the R/T machine had a developer bath time of 6.5 minutes, then the inversion and rotary times were also 6.5 minutes. All temperatures were 24C, I remember that.
Once again the results were interesting. There was a total of 5 test strips developed over 5 days in each system.
The real interesting bit was that the hand inversion gave the most dense (or developed) negatives. The R/T machine gave very good development and the density was, AFAIK, bang on the money, which pleased the boys in the lab, no end. The rotary developed negatives were just slightly different to the R/T negs in density; they were ever so slightly lighter.
The conclusion we came to, was that there does appear to be a slight increase in developing possibilities when using rotary developing. We believed the reasons the developing was so close to the tightly controlled R/T machine was due to there being less active developing agents able to effect film as the developing solution is diluted by there being less actual developer in a rotary processing tank!
All film test strips were developed in either the R/T machine, which was tightly controlled, or, in my Jobo 1520 two-reel tank.
The 1520 tank for home processing developed one Kodak test strip, one x 36 roll and one x 24 roll on the two reels. The rolls of film had all been exposed to a colour and B&W test chart, for every frame with studio flash in one in session with the same camera/lens and flash.
I developed 4 rolls and 2 test strips in one rotary and one inversion processing session each evening.
Since that time, I have always started with a new film and/or developer and used the manufacturers starting time for the first developing session after having done test exposures of a grey scale and colour chart.
Once I have correct camera exposure and correct developing time established for a film, I can, and do swap between rotary and inversion techniques, without changing my actual developing time. The final outcome is negligible; there is a difference, but not very much.
Mick Fagan's actual experience and I don't doubt its authenticity,flies in the face of the conventional wisdom and the Ilford recommendation that about 15% less dev time is needed in a rotary processor.
It prompts the comment from a newbie;"Well one of the two parties must be wrong"
I had a look at a book I have by someoen who actually ran a processing outfit using Jobo equipment who appears to back-up Mick's experience that rotary processing for the same time as hand inversion is correct. The author in question explains this by saying that his rotary processing involved a pre-wash which effectively dilutes the developer and prolongs dev time. This increase is compensated by the decrease due to constant agitation and thus manufacturers' dev time for small tanks can be taken as a good starting point.
So far so good. However he then goes on to list rotary dev times for FP4+ in ID11 stock at 6 mins which is 2.5 mins less than Ilford's hand agitation time. He quotes other times for other Ilford films and other Ilford devs which also seem to be appreciably less than Ilford hand agitation times. he calims that his negs printed normal subjects at grade 2 or 3 and he aimed for and achieved a gamma of 0.60.
I wonder how this apparent contradiction can be reconciled. No wonder newbies are confused. Could the gamma be the key?. He does go on to say that a gamma of about 0.60 will print equally well on a condenser or diffuser enlarger.
I have a CPE 2 but never attempted rotary processing of B&W so cannot speak from experience but such differences do not fill one with confidence.
Imagine buying a servicing manual for your car which said: Ensure valve clearances of a&b millimetres, then seeing another in the shops which said: ensure they are x&y millimetres!
All I can say from practical experience is that with two different colour neg kits which both gave a hand inversion sequence and a set time of 3mins 15 secs, I used the Jobo rotary processor with the same time and found the negs to be the same as I had achieved with another kit which only quoted rotary processing times.
So certainly with colour neg, any reduction in time for rotary processing would have proved detrimental to say the least.
I accept that processing instructions are starting point recommendations but its a pity that there seems to be little consensus when presumably recommendations are evidenced based.
I finally had a chance to do two tests early today and the difference between inversion and rotary processing was apparent to the naked eye.
I shot two rolls of Tri-X: one entire roll (same subject) outdoors and one entire roll of an 18% card. Each time I cut the rolls in half and developed one half by my usual inversion technique (pretty much standard) and the other half with the Jobo ATL1500. For processing times I followed Kodak's recommendations for both inversion and rotary. I followed Jobo's instructions on chemical volume.
The negatives developed with the ATL1500 seem contrastier to the naked eye. I will be printing paired negatives from both processes on the same sheet of paper next chance I get and take it from there.
One shure observation: I really like using the Jobo processor. Although I love darkroom work, processing film has always been a necessary chore for me.
The observations on this forum have been really helpful and I hope APUGers continue to share their thoughts and experiences.
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Renato, I would be quite interested in the outcome of your testing.
Very few people seem to understand that a reasonable test can be so beneficial, to your photography down the track.
I forgot to mention that in the tests I carried out, there was no pre-soaking. The reasons were, none of the lab film is ever pre-soaked, so it didn't make sense to pre-soak my home precessed film.
I have never pre-soaked film anyway.
Mick, you bring up an excellent point. In fact I found a post by Jobo stating that a pre-soak should not be used for processing with XTOL (which I used for the test). Others on APUG and photo.net have recommended a pre-soak regardless and they had the experience and results to back up their claims. I looked at the manual and for the life of me I can't figure out how to eliminate the pre-soak from Jobo's program. But I'm committed to the pre-soak step for now and continue testing until I'm reasonably satisfied/reassured. I have a grandiose and unrealistic plan to shoot boxes and bricks of negatives this Summer and need to feel like I know what I'm doing. You know the feeling...
I will appreciate further observations.
There are professional B&W Film processing labs that use Jobo Rotary processors. Considering the popularity of these processors for use with roll and sheet-films, there doesn`t seem to be much info available for use with the industry trade standard D-76 process for the popular film brands.
Just finished testing Tri-X in XTOL 1:1 today with the JOBO ATL-1500. I shot a few rolls, all pointed at the same subject, same exposure. Developed half a roll as recommended by Kodak by inversion. I then developed succeeding half rolls in the JOBO at various times (taking into account the temperature change). The one roll that came closest to the inversion roll was developed 16% less. I printed the inversion and JOBO developed negatives side by side. There is still a very faint difference, but it's the closest I could get them. Long story short: I now have a better understanding of where I stand.
Renato, that is very good news. The best part is that you have narrowed down your possible processing variations, by doing some simple testing.
I myself have a written processing sheet for every roll or sheet of film I have processed, in the last 19 years.
It may sound silly, but it sometimes amazes me when I search back for some specific processing of a film/developer combination, the information you can extract for a current situation.