Slow continuous agitation vs. Intermittent

athbr

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I'm starting to get curious about phototherms, jobos and things of the like.

Most of what I hear in these forums is that intermittent agitation > continuous. At least all the stated benefits (acutance, latitude, EI) seem to be up my alley.

Of course I can't do that with any of these devices as you can't fill up the tank to full. A few ideas that popped up in mind.

1. very slow continuous agitation
2. turning and stopping

My guess #1 would meet half way but not get quite there. #2 would be lovely if it worked but my guess is it might lead to uneven development.

Granted I probably can't set up the machine to do these things but there are some people building new products of this sort. (Shoutout to Andrew from midtone machine).

Any thoughts?
 

Kino

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Continuous agitation in one plane only tends to create directional effects; bromide drag.

You need random movement with agitation to break up the flow patterns.
 
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athbr

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Kino said:
Continuous agitation in one plane only tends to create directional effects; bromide drag.

You need random movement with agitation to break up the flow patterns.
Click to expand...

Yes indeed. But would moving very slowly in one direction than another be enough?
 

Kino

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I doubt it. It might even compound the problem. The flow of exhausted developer from a dense area under development would simply be redirected from vertical to horizontal (in the case of stand vs slow rotation).
 
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athbr

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Kino said:
I doubt it. It might even compound the problem. The flow of exhausted developer from a dense area under development would simply be redirected from vertical to horizontal (in the case of stand vs slow rotation).
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Touché. Thanks!
 

Kino

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Film has been developed for close to 100 years on spools in tanks. Random, orbital motion has always been the best bet for agitation, or someone would have standardized the methods you speak of a LONG time ago!
 

Doremus Scudder

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Rotary processors agitate continuously and do just fine for conventional processing of film (ask Bob Carnie if you don't believe me... )

So, it should be possible to come up with an agitation scheme for hand-held tanks that was continuous as well. As mentioned above, one would have to agitate randomly in order to avoid surge marks, etc. Perhaps a manual rolling agitation with directional changes or a continuous agitation with a full tank and frequent changes in agitation direction.

The question is, why would one want or need to do this. Sure, it saves some time; you can develop to a given CI more quickly with continuous agitation than with intermittent agitation, but I see no other advantages and the time savings is negligible.

The problem with continuous agitation is that it excludes the possibility of compensating effects and edge effects (those ephemeral things that all those stand developers are after ) Seriously, I've reduced the agitation frequency for the second half of my developing times in PMK just to promote the edge effects. Reducing agitation or using dilute developer as a means to control contrast and shape the film curve is a great tool. With continuous agitation, this tool is not available. Plus, if you use a developer that oxidizes rapidly, like PMK, rotary agitation will speed the oxidization and the developer may lose activity before the developing time is reached. There are strategies for dealing with this (e.g., Rollo Pyro, basically PMK with ascorbic acid added to prevent oxidation, or Bob Carnie's method of replacing the developer with fresh halfway through development).

And, regular intermittent agitation delivers great results (even if you agitate every 30 seconds and don't get any compensating or edge effects), so why the need for changing schemes?

Best,

Doremus
 
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athbr

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Hi Doremus. No disagreements here. I think you should re-read the post.

I'm not trying to agitate manual tanks continuously. Rather I was asking if it was possible to agitate rotary tanks intermittently to get the benefits you've mentioned in your post. Seems like that's not possible though.

But yes, I agree that continuous agitation of hand tanks is not a very good idea.

cheers.
 

Arvee

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I have experimented quite a bit with continuous agitation in both types of tanks: stainless tanks/reels and Paterson Super System 4 (both twirling and inversion). As DS states above, the only benefit I observed was time saved in developer. All negs came out fine (I was very careful to use a random patterns in all schemes) with a 15-20% reduction in dev time.. Really not much to be gained other than shortening the time in solution.
 
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athbr

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Again, I agree.

The matter of my concern was achieving intermittent development in rotary style automatic tanks. Not continuous development in hand style tanks.

I see that my title has lead to confusion.
 
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athbr

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Andrew O'Neill

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Rotary and dilute developers is the cat's meow...especially if you own a Jobo. Not so when you're poor, like me and have to use BTZS tubes... standing there for ages... spinning those tubes...for ages...
 

MattKing

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I use continuous agitation regularly with Paterson Super System 4 and steel reel tanks.
I believe that it helps ensure consistency, and it allows me to use smaller volumes of chemicals.
But with respect to the development stage, I don't use it for anything more than the first 30 seconds.
My reason? 120 film tends to wander when I use rotary agitation during that stage. This is particularly problematic when I load two rolls of 120 on the same reel.
The problem only manifests itself during the development stage - not the pre-wet, stop bath, fixer or HCA.
I could use it for 35mm, but I prefer to use the same process for all my films.
The Paterson tanks (plus a couple of large rubber bands) work great on a Beseler or other reversing rotary agitator.
Here is my (slightly noisy) solution for steel reels:
 

KenS

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After my 'work experience' in a Government Department where B/WLF and 35mm Ektachromes were often needed 'stat' and when 'management' 'saw the numbers/and time consumed doing it by hand agreed to invest in a Wing-Lynch processor.. It could 'do 'about E-6 rolls at a time as well as ALL the 4x5 B/W film.

Since that time I now process ALL my exposed 4x5 and 8x10 film in BTZS tubes in a "Tupperware tub filled with water 'at temperature' using my fingers to 'rotate' the tubes throughout the required development 'time. I will NEVER/EVER go back to developing my sheet film using 'hangers in tank ...or tray development.

Ken
 

Doremus Scudder

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athbr,

Sorry, I did misunderstand your goal. I guess the problem with rotary processing and intermittent agitation is that rotary systems are designed to use much less chemistry, keeping it in contact with the film by means of the continuous turning. Once you stop that, you've got some film covered and some not; not a desirable situation. Using full tanks is almost certain to overload the rotary base, however, you could agitate by hand... That, however, would waste a lot of developer.

The idea of using very dilute developer, which would then exhaust before the highlights are completely developed would certainly be an answer to getting compensating effects. A bit of testing would be in order, but it should be quite workable. You won't get any edge effects with continuous agitation even with dilute developer though. One could have different dilutions for different amounts of compensation...

I deal with taming the highlights with time adjustments and SLIMTs, so don't spend a lot of time worrying about exhaustion points and compensation. I reduce agitation primarily for the edge effects. I tray develop and get really good edge effects with PMK with agitations at one minute (once through the stack every 60 seconds) for the second half of developing. I don't need to go longer than that and risk uneven development.

Best,

Doremus
 

Bob Carnie

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Andrew O'Neill said:
Rotary and dilute developers is the cat's meow...especially if you own a Jobo. Not so when you're poor, like me and have to use BTZS tubes... standing there for ages... spinning those tubes...for ages...
Click to expand...
I have found that with Jobo's I have to stand with the machine, I have owned a bunch of them Alt2300 and now I have the CPP3 (first unit in NA btw ask Omer H) . My luck is bad and when I leave an auto program something will always go wrong. So I do everything manual on the machine and do not even hook up the water intake and outake. just turn on the machine and set the rotation speed to whatever film type and developer I am using. I fill the water jacket with water from a hose and manually fill the rinse cycles, after the process is done I take the tank off the machine and wash in a big quick dump tank I have.

Also and very important for rotary... with some developers , and with some neutral scenes with a lot of mid tone grey like skys , I will pour my chems into the tank off processor, then do a 15-30 second invert and twist and bang the tank method of rotation by hand to get the chemistry on the film as fast as possible,then put the tank on the machine and with a gray lab timer count down the time for each step.

Also I have a space beside the jobo in case of catastrophic failure( it happens) where I can mimic the rotation and with greylab and each step timed visually I can save a potential disaster ( I do not want to remember why I put this practice in place) and anyone who touches my Jobo system is trained to do this..
In a perfect world I still think stainless steel tanks and hand process is the best.. but of course it has to be done by a competent technician who does not get distracted easily .. (these days almost impossible) in fact I make all workers get their phones in another location when the work for me and now I am going to implement this policy throughout my workspace in all areas. These Iphones are the devil.


Imagine someone working on a table saw with an Iphone in one hand arguing with their better half and cutting down wood.
 

Kino

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One obscure (and frankly impractical) method of doing compensating development with ZERO agitation is to use a viscous developer coated onto the film emulsion and left in a humid chamber to develop.

The developer starves-out over the highlights but continues over the lesser exposed regions. This was the basis of the Kodak Viscomat 16mm film processor: https://archive.org/details/TNM_Vis..._Eastman_Kodak_20170911_0078/page/n1/mode/2up

Somewhere around here I have an article describing the inert compound that makes the developer viscous without impacting the developer and would be happy to dig it out if anyone expresses interest.

Just throwing this out as another historical way of doing compensating development; can't say it would be very practical without a lot of experimentation.
 

Adrian Bacon

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if you don’t want uneven development, you need to have reasonably random and vigorous agitation over the entire surface of the film.

I use a JOBO (which is continuous agitation) and control the amount of development through development time only. The agitation and temperature is constant and never changes. I have never had anything but excellent development results.

bromide drag and the various other undesirable artifacts you hear about is a result of somebody doing something wrong, usually unknowingly, and blaming a particular way of processing on said artifact.
 
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