Sensitivity curves in Cyanotypes

Discussion in 'Alternative Processes' started by philldresser, May 24, 2006.

  1. philldresser

    philldresser Subscriber

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    I would like to gain better exposure control in Cyanotypes but dont have a step wedge at the moment. So I want to know if the "Double the exposure equals a one stop increase" rule work in Cyanotypes.

    Cheers

    Phill
     
  2. RalphLambrecht

    RalphLambrecht Subscriber

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    This the reciprocity law (well almost). But I wonder if you are asking the right question, because you can double the exposure with time and aperture.

    Double the exposure (time) equals a one stop increase?
    (Yes, unless you have reciprocity failure)
    Does doubling the exposure double the density? (No)
     
  3. philldresser

    philldresser Subscriber

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    Ralph

    Thanks for the reply. I was refering to the Cyanotype exposure (UV light) which is a contact print process, so no aperture available. I just wondered if the chemicals responded reciprocally like the Silver processes do, and whether there is a heel /shoulder as well.

    Phill
     
  4. sanking

    sanking Member

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    Attached is an image file showing a cyanotype compared to a palladium curve. This curve should give you some idea of what to expect in printing cyanotype, especially as that regards the toe and the shoulder of the curve.

    Sandy
     

    Attached Files:

  5. RalphLambrecht

    RalphLambrecht Subscriber

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    Sandy

    Thanks for sharing. What software did you use to do this. Phil Davis'?
     
  6. sanking

    sanking Member

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    Hi Ralph,

    Yes, I used Davis' Winplotter program for the plot. The step wedge prints were made on COT 320 and the densities read with an X-Rite 810. I read the reflection density of the cyanotype with Red channel, and that of the palladium print with Blue channel, which I find gives a better indication of the actual depth of shadow density as seen by the eye than the Visual mode. 100% of Dmax when read this was was about 1.5 for both processes.

    Sandy
     
    Last edited by a moderator: May 26, 2006
  7. philldresser

    philldresser Subscriber

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    Thanks Sandy
    Thats exactly what I wanted to know.

    Phill

    PS Are you planning on doing any Alt Process workshops in the UK at all?
     
  8. sanking

    sanking Member

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    No plans for now but I would like to do so, assuming of course that we can get past the language problem. If you know of any organization that organizes and holds workshops of this type I woud appreciate it if you would put me in touch.

    Sandy