Effect of constant agitation?

[Tom A]

Chris, that is a nice set-up! When my current Uniroller bites the dust I think I will make something like that - big enough to hold the 5 reel tank too. The idea of using a rotisserie motor is brilliant - if it can turn a chicken - or a small lamb - it should be able to handle a 1500 ml tank too!

 

[ChrisN]

Thanks Tom! I had most of the parts on hand, but I had to visit a friend with a lathe to turn the shaft down to the right diameter. Friends with a lathe are rare and highly valued! If the weight is kept centred about the centreline, the motor does very little work.

 

[ChrisN]

A few from a second test roll.

Made today and developed in my "rotary processor". Kodak Hawkeye Traffic Surveillance film (Kodak 2485), developed in Ilford LC-29 1+100 for 1 hour with constant agitation at 3 rpm. Exposed in an old Olympus OM10 (my original, first decent camera) with 50/1.8 lens at (a dubious) 200iso. The first roll, Tri-X, showed low to medium contrast. The second showed better contrast more along the lines I'm seeking.

 

[ZeissFan]

I usually go with the recommendations. I personally don't have enough time to develop a single roll of film for two hours, so I haven't tried stand developing. Sounds interesting, but for me at this time in my life, it's too much time.

Overall, the purpose of agitation is to get fresh developer to the emulsion.

As others have said, constant agitation will increase the contrast, so you compensate by cutting the development time.

 

[degruyl]

As others have said, constant agitation will increase the contrast, so you compensate by cutting the development time.

Apparently, he also compensated by cutting the concentration.

 

[charjohncarter]

I use minimum agitation to bring the highlights under control. This is similar to stand development but without uneven development. I got this idea from 'The Negative' by Ansel Adams.

 

[tlitody]

There are 3 claimed reasons for stand development. The biggest effect is the compensating effect which restrains highlight development due to developer exhaustion. Constant agitation will lose that restraining effect completely.
The restraining effect happens because the developer in contact with the film is all used up. But at the samae time as it is used up it gives off development byproducts which contain bromides. Bromides are development inhibitors and on subject edges there will be more inhibitor produced on one side of the edge than the other. This has the the effect of enhancing edge contrast and therefore apparent sharpness which is the second claimed advantage of using stand development. Nice theory and sometimes it works. But often the developer fluid has thermal currents in it and the developer by products are moved slowly around the film surface resulting in uneven development. This is called bromide drag. Agitation not only replenishes the developer at the film surface but also disperses the by products evenly throughtout the developer thereby leading to more even development.
The third claimed benefit is increased film speed due to shadows being given extra development because the developer doesn't exhaust in the shadows. This is simply because the shadows have less halides to convert to silver.

Stand development is a relatively new idea and if it works you can get really good results. But if doesn't your negs are ruined.

So to answer the original question, I agree that around 15% less time is required compared to normal agitation procedure (not stand) as a starting point. That's what jobo suggest. And you will lose any apparent edge effects from stand development and some film speed compared to stand development. BUt you should get very evenly developed negatives.

One thing to be careful of is repeating flows in rotary agitation as these can cause uneven development. This is why auto units reverse as it gives a more randow flow pattern. The jobo expert tanks are claimed to give the most random flow pattern of all tanks.

oh forgot that constant agitation increase contrast due freshesst developer always being available at the film surface which is why you give 15% less development.

And there is no point in using very dilute developer as it will have a completely different effect than when using stand development.

 

[ChrisN]

...

And there is no point in using very dilute developer as it will have a completely different effect than when using stand development.

And different is necessarily inferior, or "wrong"? There is no point in experimenting; trying something different? 🙁

My experiments have drawn to a halt, temporarily, after the motor in the BBQ rotisserie has burned out! I have a replacement on order (ebay #190517811436, 12v 4rpm) that should be more reliable, I hope!

I did two rolls of PAN-F before the motor failed, one at 30 minutes and one at 60 minutes, with LC29 1+100, 4ml in 400ml). Both are quite usable but the second is definitely more dense overall and does show more contrast. (My enlarger works best with slightly more contrasty negs.) 45 minutes would probably be perfect, or I can experiment with a lower concentration of developer.

While the second roll (Kodak Hawkeye film) was evenly developed, the PAN-F showed some flow marks along the edge against clear sky areas, caused by either the sprocket holes or the frame of the spool. I'm now going to try a different application, with the motor turning the tank end-over-end, just like in normal inversion agitation by hand. This was actually my original plan, but I was diverted to try the Jobo arrangement. Interestingly, a 4 rpm rotation will give me 4 inversions per minute, same as the conventional pattern (as recommended by Ilford), albeit more slowly. There's still a risk that the mechanical rotation will prove to be too regular with no random movements, but I might add some vanes to the spool to encourage it to rotate a bit inside the tank!

 

[Keith]

When I first used my Paterson Orbital for 4x5 I was interested to see what the effects of constant agitation would be compared to the Combi-plan I was using.

So far with times reduced by 15-20% it's been an improvement ... especially in the evenness of the developing which is not the Combi's stong point IMO.

 

[ChrisN]

Here's a sample from each of the last two rolls; the first had 30 minutes development time, and the second had 60 minutes. Interestingly the flow marks (along the edge against the sky) are reduced in the sample with the longer time.