Dilution & Agitation

Discussion in 'B&W: Film, Paper, Chemistry' started by thefizz, Mar 15, 2005.

  1. thefizz

    thefizz Subscriber

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    Dilution: I mostly use Rodinal 1:25. If I try 1:50, what differences can I expect from my negs.

    Agitation: What will increased agitation do for my negs?


    Thanks,
    Peter
     
  2. titrisol

    titrisol Member

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    If you dilute Rodinal 1+50 or 1+100, times should be increased. our negatives will look smoother, drop contrast a bit and grain will be smaller (IMHO)

    The mlre you agitate the more contrast you create on the negative, the shorter the time you should develop.
    If you plan on diluting rodinal, you want to cut you agitation to once every other minute or so.
     
  3. modafoto

    modafoto Subscriber

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    I simply second that!
     
  4. Claire Senft

    Claire Senft Member

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    Go easy with the agitation

    The purpose of agitation is to bring new devloper into contact with the emulsion. Whatever amount of agitation is used should be gentle to prevent developer from surging thru the sproccket holes when using a film with sproket holes.
     
  5. titrisol

    titrisol Member

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    PS. I have settled for Rodinal 1+50 as standard dilution and 1+100 for EFKE 25.

     
  6. modafoto

    modafoto Subscriber

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    :tongue: 1+50 is my mantra :tongue:
     
  7. thefizz

    thefizz Subscriber

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    Thanks folks.
     
  8. Christopher Colley

    Christopher Colley Member

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    The way I understand it, though I could be corrected is in periods where no agitation is happening the developer in contact with very dense regions of the negative becomes exhausted much before the thin areas. Thus, if you leave a tank sitting the developer will work on the hilights and stop (for lack of a better word) developing the shadows very much, resulting in a lower contrast between shadow and hilight the less you agitate and more stark contrast the more you agitate because you are putting 'fresh' developer on those shadow areas.

    (experts, is this correct?)
     
  9. Donald Qualls

    Donald Qualls Member

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    The other thing you do, by increasing contrast via agitation and compensating with shorter development, is lose shadow detail. The shadows get about the same amount of development from the same time in the soup, regardless of agitation, because the developer doesn't exhaust in shadow areas (thus bringing in fresh developer has little effect in those area). So, developing longer with less agitation to get the same overall contrast will increase shadow development (which increases the real film speed). Likewise, higher dilution (which also requires longer development to obtain the same contrast) will do the same, again because even the dilute developer doesn't exhaust in the shadows.

    I've wondered if the main reason people find they need to expose at 2/3 to 1 stop under the film's rated speed isn't because they agitate too much or use too fast a process. I use a highly dilute developer, reduced agitation (10-15 seconds every 3 minutes), and develop for 3-4 times the manufacturer's times for "normal" strength developer -- and with the manufacturer's rated speed, I never have problems with lack of shadow detail unless I simply didn't give enough exposure.

    Oh, and I get these effects with TMY -- in theory, they should be stronger with "traditional" grain films like Plus-X or Tri-X; that does seem the case with J&C Pro 100, with which I've gotten excellent shadow detail.
     
  10. Will S

    Will S Member

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    Maybe. I think most developer times are too long, resulting in blocked highlights. Barry Thornton has an interesting article at:

    http://web.archive.org/web/20040202094533/www.barry-thornton.co.uk/devtime.htm

    where he outlines how to test dev time.

    Thanks,

    Will