Pyrocat dilution agitation speed, accutance relationship

Discussion in 'B&W: Film, Paper, Chemistry' started by Tom Stanworth, Jan 27, 2005.

  1. Tom Stanworth

    Tom Stanworth Member

    Sep 4, 2003
    Multi Format

    Sorry for another thread about this dev, but I have an angle. Thus far I have found the 1.5:1.5:100 dilution gives me dev times of about 10 mins at 20 degs c with 1 min agitation intervals. My questions are:

    Does increasing the interval of agitation from 1 miinute to say 3 make much difference to perceived sharpness on real prints (say a 6x7 neg enlarged to 12x9.5 or so)?

    Does constant agitation therefore considerably reduce acutance?

    How much difference does agitation have on speed, ie if one reduces agitation from 1 min intervals to 3, would this have any effect increasing film speed?

    Does dilution make real world differences to acutance as I realise it should in principle.

    Sorry for the heap of questions it is just that I want to know what direction to go in for further experimentation!

    (as an aside, asfter the Maco 100 debacle, the APX100 negs I am now getting have a liquid tonality I have never experienced before, truly wonderful; what a pisser it is no more in 5x4)
  2. sanking

    sanking Member

    Mar 26, 2003
    Large Format
    First, about film, get some Efke PL 100. It is a very nice film and not very expensive.

    About your questions.

    1. Yes, in my opinion increasing the agitation interval from one to three minutes with Pyrocat-HD should make a difference in apparent sharpness, though it may not be immediately obvious.

    2. Constant agitation does slightly decrease acutance, IMHO. However, some people prefer the rather creamy look of tonal values you get with constant agitation to the more razor line sharpness you get with reduced agitation.

    3. Dilution will not make much difference on speed. Weak dilutions and very long development times may increase effective film speed a bit with some films, but most of what we call real film speed is built into the emulsion.

    4. Type of agitation is more important than dilution in determining acutance. What you need for increased apparent sharpness is edge or adjacency effects. Edge effects develop in area of the film where the developer is exhausted, and the most effective way to produce developer exhaustion is to not renew the film with fresh developer through agitation.

    The danger is that lack of agitation is not compatible with even development. For most subjects agitation every two or three minutes is a very good compromise between the extremes.