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Thread: DIY Sensitometer

  1. #1
    Matt Alexander
    Join Date
    Nov 2017
    Location
    Wisconsin
    Posts
    86

    DIY Sensitometer

    As I've been dabbling with handmade emulsions and alt processes, I have recently been longing for standardized exposure for my plates as I test different formulas and variables. I needed a sensitometer.
    Being a die-hard DIY'er I figured this could be a project I could manage.
    I know probably the most consistent and reliable light sources we have as photographers is the strobe. At basic levels, the circuit is pretty simple, reliable and very consistent, no need for additional timers or sensors. Strobe would be ideal for this project.
    I found an example at https://www.jbhphoto.com/blog/2013/07/31/a-diy-sensitometer-really/ - there is a PDF of his project - TLDR; he uses a handle-mount flash, its way over-powered and too large. I don't have room for such a device. I needed smaller. I started looking at my shoe-mount strobes I might have available, but all ended up being too big for my needs - I needed smaller still.
    My years of photo store work reminded me of the lowly disposable camera. Tiny flash unit. It would be perfect. I picked one up after work and and got to dis-assembly. (yes I know strobe circuits can be dangerous - don't worry, I know where not to stick my tongue).
    I built the mixing chamber out of white foam-core and hot-glue and added a piece of frosted plexi to the bottom.
    Then I build an enclosure out of Black foam-core and hot glue. This allowed for a second piece of plexi for extra diffusion and created a filter chamber I can add neutral density filter as needed.
    To the base piece of plexi I taped a stouffer 21-step wedge, as well as B&W/color test patches from an old Kodak E-6 control strip (I knew saving those for all these years would come in useful someday!). I wrapped it all with gaffer tape for some added stability.

    To make things fit a bit better, I added some external switches for power and triggering.

    I'm very happy with my first tests. it works great on my slow plates, and I can easily add neutral density for faster films.

    Click image for larger version. 

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    Even monkeys fall from trees -- Japanese proverb

  2. #2

    Join Date
    Dec 2009
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    Pacifica, CA
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    Re: DIY Sensitometer

    Looks like it works!

  3. #3
    ic-racer's Avatar
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    Feb 2007
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    6,201

    Re: DIY Sensitometer

    The most difficult part can be getting even exposure across the field. Did you do a test exposure with ND filter only and check edge vs center. If it is not even, you could figure where each step lies and apply a correction factor to your step densities.

  4. #4
    Tin Can's Avatar
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    Dec 2011
    Posts
    18,952

    Re: DIY Sensitometer

    Very GOOD!

    Love DIY

    JB is a long time member here and his many tutorials ARE handy

    Find them on the link
    Tin Can

  5. #5
    Matt Alexander
    Join Date
    Nov 2017
    Location
    Wisconsin
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    Re: DIY Sensitometer

    Quote Originally Posted by Tin Can View Post
    Very GOOD!

    Love DIY

    JB is a long time member here and his many tutorials ARE handy

    Find them on the link
    Thanks!
    I enjoy your many DIY posts. JB indeed has many good things on his site too - it was a great proof-of-concept jumping off point for this project.
    Even monkeys fall from trees -- Japanese proverb

  6. #6
    Matt Alexander
    Join Date
    Nov 2017
    Location
    Wisconsin
    Posts
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    Re: DIY Sensitometer

    Quote Originally Posted by ic-racer View Post
    The most difficult part can be getting even exposure across the field. Did you do a test exposure with ND filter only and check edge vs center. If it is not even, you could figure where each step lies and apply a correction factor to your step densities.
    Indeed. My early version only had mixing chamber + frosted plexi and that was a bit hot in the center. But adding the second layer of plexi with an inch or so gap between evened things out pretty well. That gap also creates a filter drawer where I can add additional diffusion or correction if needed.
    Even monkeys fall from trees -- Japanese proverb

  7. #7

    Join Date
    Feb 2015
    Location
    Sheridan, Colorado
    Posts
    1,647

    Re: DIY Sensitometer

    You should consider posting it on INSTRUCTABLES.com

    Instructables is a community for people who like to make things. Come explore, share, and make your next project with us!

    https://www.instructables.com/

    I made an INSTRUCTABLE myself -- not for anything photographic, but for a:

    Almost Free, Portable, Indoor, Home-made Evaporative (Swamp) Cooler

    BUT, they do have a lot of photographic DIY ideas!!!!

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