Reducing Agitation - Effect on development time

I'm trying to understand how development times should change (in general) as a function of reducing agitation. We know, for instance, that we reduce development time by about 15% for constant agitation (from a regular agitation regiment of say once per minute). What factor would we apply if we instead agitate every other minute? Every fourth minute?

Second question: Consider a semi-stand situation where a 30 minute development time, with agitation at 10 and 20 minutes, produces a well-developed negative (however you want to define that). What difference would I expect to see if I moved those two agitation cycles to minutes 5 and 10? Or to 20 and 25? Forget practical issues for now (uneven development, drag, etc.). I’m interested to know the effect of "agitation spacing" on contrast and density.

I don't want to get hung up on details here. Obviously there are a lot of variables, and this is all subject to testing. My questions are theoretical ones to better understand how agitation frequency affects overall development.

Thanks.

I recall from a post many years ago by Dave Miller who was once a prominent member here who said that he had attended a short course given by Les McLean on film and print processing who wrote the book "Creative Black and White Photography" that Les had some of the participants develop with the recommended manufacturer's agitation regime and others use what he called " the cocktail waiter's agitation i.e. very vigorous . The difference in the negs made about a half grade difference in the correct grade for the print. He may or may not have stated it but I took him to mean that the developer was the same for both groups

pentaxuser

Minor White wrote about this in The New Zone System Manual (mid-70s edition). Very basically, expose for Zone V, development time/temperature for the shadow areas, and agitation for the highlights.
Phil Davis also considered this in devising the algorithm in BEyond The Zone System. His exposure and development times change based on the subject brightness range of the scene.
I'm not sure you can successfully apply something as simple as a factor.
Because of the high brightness range where I live, I use a minimal agitation scheme to compress the range a bit. I had to determine development times through BTZS measurements for sheet film, and through trial and error testing for roll film.
I know this is not much of an answer, but you might read the two mentioned books.

As you already said, lots of variables involved here. However, in general one benefit of reduced agitation is greater creation of edge effects which can lead to the impression of greater acutance in the film. I used to develop all my LF film in Jobo Expert Drums, but fairly recently started doing EMA (extreme minimal agitation) in homemade tubes. I can tell you that the negatives I produce now reveal a crispness (micro-contrast) unseen in the rotary developed negatives. Eberhard effect? Whatever it is, I like the result!

My recollection is that minimal agitation adds 50% to development time. Minimal is NOT semi-stand, but precisely what you are talking about: 30-60 seconds initially followed by 10-15 seconds every 3rd minute. Adams discusses this in "The Negative". I've used this approach with Pyrocat-HD and HC-110 (even 1:100 dilution) and been very pleased with the outcomes. I have not tried to fine tune the time at this point because I haven't done any "testing", but I do intend to do so. My guess is that the "best" add-on time might tend to be less than what I've used.

I think of it as total development time leads to overall density. Agitation affects contrast, or density distribution. So in my mind I don't mix the two ideas. I generally develop at recommended times for a chosen dilution. I agitate as little as possible to avoid bromine drag.

chassis said:

. I agitate as little as possible to avoid bromine drag.

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Isn't bromide drag the result of too little agitation such as what you are liable to get in stand development? If little agitation give you what you want then fine but unless I have misunderstood the causes of bromide drag I think you need not worry about normal as in manufacturers' recommended agitation.

pentaxuser

pentaxuser said:

Isn't bromide drag the result of too little agitation such as what you are liable to get in stand development? If little agitation give you what you want then fine but unless I have misunderstood the causes of bromide drag I think you need not worry about normal as in manufacturers' recommended agitation.

pentaxuser

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pentaxuser, please forgive my poor choice in words. I meant to say, "I agitate as little as possible, while avoiding bromine drag."

I have experience with zero agitation development, with resulting strong drag effects in the negative. My preference is to agitate just enough, but not more than required, to avoid bromine drag. English was not my field of study, so apologies if this is unnecessarily confusing.

chassis said:

I have experience with zero agitation development, with resulting strong drag effects in the negative. My preference is to agitate just enough, but not more than required, to avoid bromine drag. English was not my field of study, so apologies if this is unnecessarily confusing.

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Well these were some of the practical issues I didn't want to get into, but it's kind of what I'm after too. That is, reducing agitation as much as possible to lift the shadows while avoiding drag. The "sweet spot" seems to be about three minutes. After three minutes, I can usually spot drag marks around the sprocket holes. I'm using HC-110 and HP5+ for these exercises.

JWMster said:

My recollection is that minimal agitation adds 50% to development time. Minimal is NOT semi-stand, but precisely what you are talking about: 30-60 seconds initially followed by 10-15 seconds every 3rd minute.

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Right. I'm talking about something between regular agitation (every 60 seconds) and semi-stand (once about halfway), although in some sources, semi-stand is used to describe a few agitation cycles (two, three at the most).

So the mathematician in me is thinking that if constant agitation is a 15% reduction in time, and if agitation every three minutes is (as you say) an increase of 50%, that these data points can be graphed (development time as a function of agitation frequency). The graphs will obviously look different for different film and developer combinations (all else the same), but I would expect the shapes of all these graphs to be very similar.

That clears it up. Your experience suggests, as does the experiment conducted by Les McLean and his students, that a range of agitations may make very little difference. All agitation is doing is replacing fresh developer for the stuff on the film which is getting exhausted. As exhaustion isn't instant it does beg the question of whether one twist and inversion agitation every 30 secs might well be as good as the Kodak recommendation of about 3 times for 5 secs.

Cowardice has always prevented me from trying this .....in case If everyone was this cautious I might not be talking to you as the U.S. would still be unknown and DT would have been born in Scotland and still live there.

We have to be grateful for the adventurers

pentaxuser

I expect that any conclusions that might be reached would vary with every type of film, and every type of developer, and every type of developer.
In other words, if you do experiments with your favourite film, your favourite developer, and your favourite type of agitation, you may be able to develop a rule that is particular to your circumstances.
A general rule? Not so likely.

Alan9940 said:

As you already said, lots of variables involved here. However, in general one benefit of reduced agitation is greater creation of edge effects which can lead to the impression of greater acutance in the film. I used to develop all my LF film in Jobo Expert Drums, but fairly recently started doing EMA (extreme minimal agitation) in homemade tubes. I can tell you that the negatives I produce now reveal a crispness (micro-contrast) unseen in the rotary developed negatives. Eberhard effect? Whatever it is, I like the result!

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Many years before I bought a Jobo processor, an old timer photographer told me that Jobo rotary processing produced good even development but hurt contrast because it was "constant agitation". That made sense to me then and even more sense now due to the fact that fresh developer is always in contact with the film. I would think that if a person could discover how long it takes your developer, that is in contact with the film, to be exhausted before agitating, your question would be answered. To be safe, I would probably agitate once a minute or even once every two minutes. Does that sound reasonable to any one else? Total developing time would remain the same as what the manufacturer recommends for non Jobo processing. By the way, I don't do color.........Regards!

In its heyday Jobo recommended a 15% reduction in developing times for films processed with constant agitation. I bought a pair of Duolabs in 2003 and did some quite exensive tests as I wanted to get consistent results(in the "old" Gamma 5.6-6.0 range -I'm sure the older members of this forum will know all about Gamma.

In 2010 or 2011 one of the pair of Jobo photo technicians who devised the Duolab told me the -15% virtually guaranteed consistent results at about Gamma 5.8 and to increase Gamma by 0.2 points I should process at -10%, -5% and -2% for 5.8, 6.0 and 6.2. He also confirmed what oldtimertoo wrote about constant agitation in #12.

The best thing about constant agitation is that it removes most of the variables in film processing and standardises everything into one neat and tidy technique. The only flaw I have found is that some developers (Beutlers, Thornton's Two Bath) produce their best work on minimal agitation. I cannot speak for Beutler's as I don't use it, but I have processed many films in the Thornton's two bath with constant agitation at -15%, with entirely satisfactory results for my need.s

In summary, I have always followed Jobo's advice to a point as it makes my life in the darkroom much easier and I have found the -15% produces exactly the results I want.

Very interested in this discussion. Of course the newer tech Filmomat.eu machine seems to offer a lot, but at a high price. For now, I' secured the prospect of some potentail auto-agitation with an old Uniroller, but have found manual agitation just fine.... if not a tad time consuming. Please keep the posts coming!!!

Trying to control density and contrast by changing agitation is sort of a bassackards way of doing things. Stick with changing development time for the most consistent results.

Gerald C Koch said:

Trying to control density and contrast by changing agitation is sort of a bassackards way of doing things. Stick with changing development time for the most consistent results.

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I'm not asking how to do things, I'm asking how these things work.

bvy said:

I'm not asking how to do things, I'm asking how these things work.

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Development is a diffusion controlled process. Increasing agitation brings fresh developer to the film surface where it is absorbed thereby increasing development. In this process used developer is also removed from the film. In other words fresh developer is exchanged for used developer..

The Film Developing Cookbook by Anchell and Troop has a few paragraphs on this on p33 .
As posted above 50% time increase is suggested for 3 min agitation intervals.
Glycin is noted for minimising streaks.

I'm running a poll on Agitation (Hand vs. Machine aka "Jobo" or other) on Rangefinder Forum. Hesitate to repeat it here. Just kind of curious as there seem to be far more folks using Jobos here than there, just as there are more folks using Pyrocat-HD here than there. But then I've been surprised that some folks just toss of the fact that they're using a Jobo or a Hassy scanner... like it's nothing. Anyway.... may the mileaqe vary and the Force be with us all.

I favor hand agitation as the little bit of randomness helps prevent such things a surge marks, bromide drag, etc. Back when most film was machine processed the nitrogen burst agitation helped add some randomness to the process.