Moss1310
Newbie
Hi. New to developing film and have a question. What do different levels of agitation do to the final result? I.e gentle vs. more vigorous... Does it matter by the film and developer used? Thanks for your help.
Agitation question
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Roger Hicks
Veteran
Gentler = slower development (increase time to compensate), higher edge sharpness, lower film speed for a given contrast. You'll see bigger differences with long development times in weak developers, less difference in shorter times with stronger, more aggressive developers. The basic truth, though, is that all differences resulting from variations in anything resembling normal agitation (i.e. anything above 'semi-stand' development) are pretty minor -- certainly, far smaller than a perusal of Internet claims might lead you to believe.
Cheers,
R.
Cheers,
R.
AlexisNeel
http://alexisneel.com/
Agitation controls contrast, for the most part, and time increases density, for the most part. Both play on the other to an extent but that is basic jist of it. When you agitate, you are running fresher dev. over the film, which allows that fresher dev. to do its work more on areas of the film with more silver exposed. It also helps the shadow area by getting fresher dev. on that part of the film, bringing out the subtle exposed areas as well. IF the dev. was allowed to not be refreshed, it would exhaust itself and not continue to dev. the film at the pace it does with fresher dev. is washed over that area, and so when fresher dev. is allowed to replenish the film, the areas with the higher exposure of silver dev. at a faster rate than the areas with less silver exposure, thus increasing your contrast. And because of this, there is a slight increase in density as well, so sometimes an adjustment if dev. time (downward) is needed, though in my opinion, it is better to have a slightly denser neg than a less dense one.
Alexis
alexisneel.com
Alexis
alexisneel.com
Roger Hicks
Veteran
Note that not everyone agrees with Alexis's interpretation of the relationship between contrast, density, agitation and time: see http://www.rangefinderforum.com/forums/showthread.php?t=130003
Cheers,
R.
Cheers,
R.
sevo
Fokutorendaburando
That is a inappropriate generalization of the behaviour of a few rather peculiar developers (namely Rodinal and Beutler), and quite wrong in just about every other case. Time, agitation, temperature and concentration all primarily affect density.
In low concentration developers depletion effects occur, and the localization of these can within limits be controlled by the agitation regime. But that is no matter of contrast as a whole. The proper term for a edge contrast increase is acutance - which can be created in a variety of ways, in our case by chemical edge acceleration/inhibition, but also through overcorrecting the lens or applying a optical or calculated/simulated unsharp mask.
Terry Christian
Established
Good posts above, but in case the OP's real question is how he should agitate:
Agitate gently but thoroughly -- nice slow inversions if you're using an inversion tank, twisting a bit as you invert. Too vigorous agitation can exacerbate problems with air bubbles, and can cause surge marks around sprocket holes. Too little agitation can result in underdevelopment. Most developers/films call for 10 secs. of agitation at the beginning and 5 secs. each additional minute, though this can vary.
Agitate gently but thoroughly -- nice slow inversions if you're using an inversion tank, twisting a bit as you invert. Too vigorous agitation can exacerbate problems with air bubbles, and can cause surge marks around sprocket holes. Too little agitation can result in underdevelopment. Most developers/films call for 10 secs. of agitation at the beginning and 5 secs. each additional minute, though this can vary.
Roger Hicks
Veteran
Dear Terry,
Not really.
Continuous agitation is perfectly feasible and indeed is the norm with e.g. Jobo CPEs. Surge marks are normally caused by agitating in one direction only (not enough randomness). Bubbles will not not normally form or stick on wet emulsion, only as the film is first wetted, hence the 'bang on the table' to lose bubbles after filling the tank. Normal agitation is either 10 sec/minute or 5/sec every 30 sec, often with an initial 30 seconds constant.
None of it matters very much. Agitation is either adequate or not -- and 'inadequate' normally means uneven development, not under-development, as reduced agitation can be compensated for by additional time. What is important is consistency: I use 30 sec initially plus 10 sec/min (8 twisting inversions), but if I switched to 5 sec every 30 sec the difference would not be great. Sensitometric agitation is traditionally with a brush...
Cheers,
R.
V-12
Well-known
I'm not sold on the idea that banging the tank on the worktop dissipates bubbles. I generally go for an inversion and a swirl.
Terry Christian
Established
I'm by no means arguing with continuous agitation, Roger -- I was only mentioning the type of agitation most newbies like the OP are most likely to use with a hand processing tank. Of course there are other schemes and methods.
Fotohuis
Well-known
zauhar
Veteran
I have followed the Massive Dev Chart app, and carry out 1 minute agitation with twirl stick, followed by 10 sec every minute.
However, I have definitely been over-agitating, especially when pushing film. I have maintained the 1 minute initial, but now do 10 sec every other minute during long development times (like 10 minutes).
I seem to be alone in doing a full minute initial agitation, but I am also alone in using the stick as opposed to inversions.
Randy
However, I have definitely been over-agitating, especially when pushing film. I have maintained the 1 minute initial, but now do 10 sec every other minute during long development times (like 10 minutes).
I seem to be alone in doing a full minute initial agitation, but I am also alone in using the stick as opposed to inversions.
Randy
ibcrewin
Ah looky looky
I like to whack the bottom of the can with my hand, Invert the can , twist the can clock wise and back down. I do thins 3-4x in a 5 sec period. Then set it down until the next agitation is scheduled.
Roger Hicks
Veteran
Sorry: didn't mean to come across as combative. Though as I say, I'd double your recommendations (and so would Ilford, as far as I recall). My recommendation is one end of 'normal'; yours, the other. Either way, the effects are minor. Consistency is always the key.
Cheers,
R.
Roger Hicks
Veteran
Dunno. Tried it with scrap film and it's persuasive... But I do the bang in the middle of (or early in) the 30 seconds initial inversions and swirls.
Cheers,
R.
Roger Hicks
Veteran
Dear Randy,
What leads you to say you were over-agitating before? I'm not arguing with your approach -- the whole thing is intensely personal -- but I'd be interested in the reasons for your decision.
Cheers,
R.
notraces
Bob Smith
If you'd like a great film reference book -- I highly recommend this: http://x2t.com/Film-Cookbook
You'll find all kinds of very useful information - including discussion with regards to various agitation methods.
You'll find all kinds of very useful information - including discussion with regards to various agitation methods.
rkm
Well-known
Roger,
I've been having issues with bubbles leaving circular development marks on the last half dozen negs of each roll. I've been banging the tank on the table more and more aggressively (at the end of each cycle of inversions, including the first 30 seconds) but the problem still persists. I'm guessing I need to do as you suggest, and bang the tank soon after being filled, rather than waiting to the end of the 30 seconds of inversions. However, is there any sense in pre-wetting the film before adding the developer, to prevent these initial bubbles from sticking?
V-12
Well-known
Air bubbles form when the developer froths. Inversion agitation causes the developer to froth. Swirling, either with the Paterson 'stick' or a gentle rotation of the tank will not cause air bubbles. But, swirling alone will not evenly distribute the developer or keep it mixed in some cases, so inversion is still required.
Banging the tank relies on the bubbles breaking free and going 'up'. But you can't guarantee that, especially if you have more than one reel in the tank, so how many times do you need to bang it to get the bubbles up from bottom to top? Swirling causes the bubbles to find a way out of the liquid over a slightly longer cycle, as the liquid rotates the bubbles rise to each level and then out into the atmosphere within the tank.
So the ideal is to invert (to keep fresh developer on the film and fully mixed) and swirl at the end to allow the bubbles to find a way up and out.
Banging the tank relies on the bubbles breaking free and going 'up'. But you can't guarantee that, especially if you have more than one reel in the tank, so how many times do you need to bang it to get the bubbles up from bottom to top? Swirling causes the bubbles to find a way out of the liquid over a slightly longer cycle, as the liquid rotates the bubbles rise to each level and then out into the atmosphere within the tank.
So the ideal is to invert (to keep fresh developer on the film and fully mixed) and swirl at the end to allow the bubbles to find a way up and out.
Roger Hicks
Veteran
My suspicion is that if anything, pre-wetting will increase the problem, not reduce it. Why, after all, should plain water be any less bubbly than developer? On the other hand, I suppose that a good shake and drain should wet the film evenly. In other words, I just don't know the answer.
Yes, I'd go for the bang as soon as possible after filling, but I never bang after that, and I've not had any problems in 40 years or more. In fact, I'd not even heard of bubbles being a problem for many years, and I assumed that this was because modern films contain all kinds of clever additives to reduce the risk. What film(s) are you having problems with?
Cheers,
R.
Roger Hicks
Veteran
Highlight: very true, but froth-bubbles shouldn't stick to wet film, and unless they're stuck to the film, they'll rise pretty fast anyway.
You can agitate perfectly satisfactorily with swirl only, or by moving the film up and down in a deep tank: I've done both.
Cheers,
R.
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