Densitometer: alternative calibration targets

Discussion in 'B&W: Film, Paper, Chemistry' started by Robland, Apr 3, 2009.

  1. Robland

    Robland Member

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    I acquired an X-Rite 811 densitometer and their website wants $110 for the transmission and reflection calibration targets. The reflection target looks nothing more than white/black/grey dots on a small card. The transmission is a 4 step wedge (I assume transparency/slide).

    I want to use Stouffer's 21 step targets (Reflection and Transmission), but which 3 or 4 would I use for calibration. I like the idea of the Stouffer products since they have other uses and they are $6.55 each.
     
  2. L Gebhardt

    L Gebhardt Subscriber

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    The reflection target is actually a metal plate coated with enamel. So I can see how it's expensive. Any item with approximately the correct values should work. On my 810 I can input what the calibration targets' values are.

    Each color channel varies by a few points but, for reflection they are about:

    White .08
    Grey .95
    black 1.8


    The transmission target is:
    Linearity 4 3.7
    Cal HI 3.0
    Linearity 2 1.47
    Linearity 1 .23

    Those values might help you in finding a suitable substitute.
     
  3. Mike Wilde

    Mike Wilde Member

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    Stouffer 21 step is half a stop scale, Dlog=0.15 per step, so you can use the first clearsectio as base fog, and zero on that, and then verify that , say 4 setps in you are reading close to .60. Stoffer sell calibrated step wedges, but is it really that important how precise you are?

    I don' have a reflective densitometer ( I was freely given an old TD-504) When I am calibrating for alt processe, etc., I contact print the step wedge onto a sample piece of sensitised material, then process and dry it. Using a portion of the un-exposed but sensitized material, I zero the transmission unit, and read through the paper base to get how linera the step wedge is. This gives me a good idea of what contrast index that negatives should be made to to print well onto any particular alt process.