HP5 Reciprocity failure and development contraction

Discussion in 'Pinhole Photography' started by NickG, Dec 12, 2010.

  1. NickG

    NickG Member

    Messages:
    8
    Joined:
    Oct 13, 2008
    Location:
    St Leonards
    Shooter:
    Medium Format
    I shoot with HP5 but have little experience of using it for v. long exposures. I know the reciprocity law but not sure about how much to reduce development by with v long exposures...

    Any hard and fast rule about this? Can anyone help?

    Cheers,

    Nick.
     
  2. ic-racer

    ic-racer Member

    Messages:
    7,441
    Joined:
    Feb 25, 2007
    Location:
    Midwest USA
    Shooter:
    Multi Format
    Are you printing with multigrade paper? If so, I'd not make any changes in development unless you run out of yellow/green when printing. If you run out of yellow/green then decrease development by 20%. The graph on the HP5 datasheet ends at 30 seconds so beyond that any development compensation is pretty much trial and error depending on the duration of exposure and scene range.

    If you need exposure compensation beyond the 30 sec range listed, there are some equations posted by Lee L who is one of the resident experts on reciprocity.
     
    Last edited by a moderator: Dec 12, 2010
  3. NickG

    NickG Member

    Messages:
    8
    Joined:
    Oct 13, 2008
    Location:
    St Leonards
    Shooter:
    Medium Format
    Thanks - good article. Found a great one by Howard Bond which Lee L recommended. Cheers