Exposure monitor

Discussion in 'Darkroom Equipment' started by Boris Mirkov, Oct 18, 2012.

  1. Boris Mirkov

    Boris Mirkov Member

    Nov 12, 2009
    Serbia, Belgrade
    Multi Format
    Can I get some help on how to use this thing? Paper grades here are marked as letters but on the box are marked as numbers, and is it possible to calibrate it?

    Attached Files:

  2. Mike Wilde

    Mike Wilde Member

    Aug 10, 2006
    Multi Format
    This exposure monitor does not directly read contrast.

    Make a good print that you like the contrast range and has a good selection of light just off white tones. Dont change anything.
    Set the time on the exposure monitor to match the time you exposed the tests print to.
    Now place the monitor sensor eye area under the enlarger, at an area where you want to be able to have reproducable tone. For me it iis the first hint of non white in the print.
    (No safe lights at this stage). Turn the lettered dial until the inicator light either just lights or just extinguishes. Turn safelights on at this stage and see if anything chages. That tells you if your safelights cause a problem to the meter.

    Some people do this with all MG filters pulled, and then figure out filter factors after the fact. Othere figure out that the 0-3 ones let the meter be close enough. Test this for yourself.

    You likely can use this thing to figure out contrast range of the paper. The letter dial is likely a stop or half a stop per letter increment.
    With your test setting double the time dial, and close the lens a stop and the balance light should be close to tripping. Not all lens stops are precisely right.
    Then go back to the original aperture and see how many steps on the letter dial to move to bring the indicator back to balancing.

    It all sounds more confusing than just fiddling with it.

    Now you have your reference for that paper, and developer time, temperature, dilution and freshness. Try to be consitent with the developer time and temp.
    Once you know how many letter steps per stop you can start to figure negative contrast range, and then the paper to match it.

    Set up your negative in the enlarger and project it.
    Get the letters set mid range on the exposure monitor, and set an arbitrary time to make it balance on the thinnest part of the negative where you want shadow detial, and not just featureless black.
    Now slide the probe eye to the densest part of the neg, where you want highlight detail and not just plain white. Without changing the time, step though the letters and keep track of how many steps to make the bridge balance.

    Say for example each step was half a stop. In log density terms that is 0.15. You find a 7 step range in your negative between detailed shadows and detailed highlights. So 7x0.15 = 1.05LogD- ISO Paper ranges are just 100X this - so you need a paper range rated for 105, or a MG filter that will give a 105 response to the multigrade paper.

    I hope this explanation helps.