jobo test printer

Discussion in 'Enlarging' started by doc4x5, Aug 23, 2005.

  1. doc4x5

    doc4x5 Member

    Messages:
    27
    Joined:
    Nov 13, 2004
    Location:
    Portland, Or
    Shooter:
    4x5 Format
    I recently just started reading Steve Anchell's excellent book on variable contrast printing. In it he mentions and shows the Jobo test strip printer and how to use it to make test strip prints. I was looking through my darkroom and came upon one. It has separate sections each of which has different density, and numbers 1 through 5. I looked at the Jobo website and searched the web and have been unable to find what the numbers correspond to. I can certainly run a few tests but would appreciate it if someone who uses it could simply tell me what the ratios are, eg if I expose the sheet for a minute, how many seconds do each segment represent? I posted this on photonet as well

    Thanks so much.

    Eric
     
  2. fotogray

    fotogray Member

    Messages:
    1
    Joined:
    Aug 22, 2005
    Location:
    Napa Valley
    Shooter:
    Multi Format
    Jobo test strip

    Each segment would represent 1/5,2/5,3/5,4/5,5/5ths of your total exposure time. A test exposure of 20 seconds would be equal to 4,8,12,16 and 20 second test strips!
     
  3. doc4x5

    doc4x5 Member

    Messages:
    27
    Joined:
    Nov 13, 2004
    Location:
    Portland, Or
    Shooter:
    4x5 Format
    Thanks so much. I'm off to the darkroom, even on a beautiful day here in Oregon, to try it out.
     
  4. Seele

    Seele Member

    Messages:
    194
    Joined:
    Feb 2, 2004
    Location:
    Sydney Austr
    I have tried a number of these test strip printers, and the only one which works is the Durst: a strip of paper is cut to a suitable width and feed into it, which is like a light-tight sleeve. The paper can then be pulled through this and a small section is exposed each time, therefore, the same part of the image is printed every time. It also means that you can vary exposure or even filtration at every test exposure, and this can be read very easily on the resultant test strip.

    Coupled with a Wallner timer which uses a log scale on its time dial this makes a great combination where pin-point accuracy and consistency can be achieved. It is a pity that Durst stopped making it quite some time ago.
     
  5. pentaxuser

    pentaxuser Subscriber

    Messages:
    8,256
    Joined:
    May 9, 2005
    Location:
    Daventry, No
    Shooter:
    35mm
    I found this to be very useful for colour printing when used with a 4 section Comask. My test strip was a full 10x8 inches with the 5 strips repeated for each half of a 10x8 so each 4x5 inch had an identical copy of the 5 strip test printer in it and could be combined with 4 different magenta and yellow combinations. That way an accurate colour print with accurate exposure could be produced in as little as one test 10x8 test print. This can then be used to calibrate a colour analyser

    I have never used it for B&W but thinking about it I suppose it could be used in theory for 20 different exposures for supreme accuracy and combined with 4 different contrast grades.

    The only problem is that the strips run horizontally so each strip does not to cover a representative section of the negative which a diagonal strip might. The top two, say, give sky only readings then middle ground then foreground. However with potentially 20 different exposures and 4 different contrasts in B&W it should be possible to cherry pick the right exposures and contrasts for each section to allow for burning and dodging.

    For average prints there are probably quicker, easier and cheaper methods such as the Paterson 5 strip test printer using a 5x4 paper which allows the same section of a neg to be printed at exposures set by the printer whereas the Jobo strips are pre-set at intervals deterimined by initial exposure.

    Pentaxuser