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Thread: Agitation: Intermittent inversions VS continuous rotary

  1. #21
    Thalmees's Avatar
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    Re: Agitation: Intermittent inversions VS continuous rotary

    Great dialogue.
    Wondering if the motor speed of Jobo, has some pull effect if slowed below 4?
    Say: 2 motor speed or even 1? after initial 1 min or so on 4 to avoid any discrepancies in solution flow over the film.

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  2. #22

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    Re: Agitation: Intermittent inversions VS continuous rotary

    Mine only has two speeds, but at the higher speed, I get uneven development. This is a well known issue I believe. The slow speed is something like 30rpm. I don't think even slower will influence acutance/compensation as even at 2rpm the developer will be in constant motion and therefore local exhaustion will not take place. If it does, it's bound to be irregular due to laminar flow and therefore undesirable.

  3. #23

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    Re: Agitation: Intermittent inversions VS continuous rotary

    Quote Originally Posted by Thalmees View Post
    Wondering if the motor speed of Jobo, has some pull effect if slowed below 4?
    Say: 2 motor speed or even 1? after initial 1 min or so on 4 to avoid any discrepancies in solution flow over the film.
    I also agree with koraks, this can be tested by just developing two contact copies of the stouffer wedge to compare, but I guess that with constant agitation we have always fresh enough developer inside the emulsion, so my guess is that there is no difference.



    Quote Originally Posted by koraks View Post
    Mine only has two speeds, but at the higher speed, I get uneven development. This is a well known issue I believe. The slow speed is something like 30rpm. I don't think even slower will influence acutance/compensation as even at 2rpm the developer will be in constant motion and therefore local exhaustion will not take place. If it does, it's bound to be irregular due to laminar flow and therefore undesirable.

    I agree, beyond that Eberhard and Kotinsky effects can be better noticed in small formats, IIRC I read that when Agfa realized that adjacency effects existed they changed recommendation from agitating each 30s to 1min. But with constant agitation those effects should not be noticed.

    IIRC it's about local deveoper exhaustion but also about removing the by-products that are also retarding development if present, as bromide drags show when that happens.

  4. #24
    Peter De Smidt's Avatar
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    Re: Agitation: Intermittent inversions VS continuous rotary

    Sure, slowing the drum down will have some effect. Pyro formulas oxidize less, for example, if using the slowest speed. My 20 year old cpp-2, though, get's a little sketchy at the slowest speed. Sometimes it'll stop rotating, you can imagine the panic!, and so I run it slightly higher.

    With edge effects, more isn't necessarily better, and they have less of an effect with the low magnification prints most of use produce with LF negatives. A number of years ago, I developed some film semi-stand in Fx-1, just to see what all of the hub bub about edges effects was about. Sure enough, I got major edges effects on the 35mm film. Blown up to 8x0 there was an obvious difference from my regular development technique/developer. But it wasn't better for my purposes, except, perhaps for very special circumstances. Of course there's more to semi-stand than edge effects, and some people clearly get great results with it....for their purposes. It's similar to unsharp masking in the sense that some will love the results and others won't. Howard Bond loved it, as did many other people, but some found the results unnatural. These are just tools and techniques that give different results. Better? That's up to you. "Museum" quality can obviously be achieved in many ways.
    Last edited by Peter De Smidt; 23-Aug-2018 at 12:04.
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  5. #25
    bob carnie's Avatar
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    Re: Agitation: Intermittent inversions VS continuous rotary

    I am sure Brassai and Sanders did not agonize over this, their work is pretty good IMO.

    I agree with Peter many ways to create, some of the nicest negatives in BW to print have been those type 55 polaroid negs.

    just sayin

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