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Thread: Need Guidance on Getting a Sensitometer

  1. #11

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    Re: Need Guidance on Getting a Densitometer

    Hi, being new to this, I was thinking a sensitometer would simplify the exposure process of the step wedge by not having to expose a test wedge and then either use a lux meter or convert EV values to lux of the exposure light source to ultimately create the characteristic curves, etc.

    I did find this interesting thread about various sensitometers used on B&W films:
    Color of Light in Sensitometer Tests by IC-Racer
    https://www.photrio.com/forum/thread...hootout.95837/

    I was originally thinking about making an in camera 4x5 sheet film 21 step Stouffer step wedge exposure by placing the Stouffer wedge in front of a sheet of test film in the film holder and then setting the lens to infinity and exposing the film against at white board at +5 stops (Zone 10) in open shade at various EI ratings. I think I read about this on Paul Wainwright's website first. I have used this method for finding the true film speed of my film and developer combinations and for establishing N, N+ and N- development times, but never for plotting the 21 densities for the purpose of creating characteristic curves. Maybe that approach is valid, or there is a better approach using an enlarger maybe? Anyone here shed some light on this with your experience?




    Quote Originally Posted by Oren Grad View Post
    Larry, the error was mine, not yours. I've reset the thread title accordingly, and I apologize for the grief it caused you.

    FWIW, I can't recall reading about any still photographer using a sensitometer to expose film for these tests - it's always been a step tablet and/or carefully timed direct exposures to light. The methods Phil Davis describes in the various editions of "Beyond the Zone System" are par for the course. The only references I can find to sensitometers relate to use for X-ray and cine film process control in a commercial setting. I'm happy to be corrected if someone can point to documentation. But if you can lay your hands on one inexpensively enough, and can figure out how to check its calibration...

  2. #12

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    Re: Need Guidance on Getting a Densitometer

    That seems to be the path that is most likely I think.

    The one question I have is how would you know where to start with an exposure time using the enlarger light source for the step wedge contact exposure?

    Would you do some trial and error exposure and development tests to find a test strip that has good tonal separation across the 21 steps or is there a better approach?

    Also, this would have to be done in total darkroom since I would be exposing B&W panchromatic film.

    Quote Originally Posted by Oren Grad View Post
    And a follow-up: I've now read page 5 of that Kodak workbook and I see where this is coming from. Everyone I know who has done this procedure for themselves has made the required exposures simply by contact printing a step tablet under an enlarger.

  3. #13
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    Re: Need Guidance on Getting a Densitometer

    Quote Originally Posted by LFLarry View Post
    I did find this interesting thread about various sensitometers used on B&W films:
    Color of Light in Sensitometer Tests by IC-Racer
    https://www.photrio.com/forum/thread...hootout.95837/
    Thanks for that link!

    As you're figuring out what will work best for you, do take a look at "Beyond the Zone System" if you haven't already - the current edition is pricey but earlier editions are available inexpensively on AbeBooks. Phil described his procedures in detail.

  4. #14

    Re: Need Guidance on Getting a Sensitometer

    Art of Pyro Zone Board by Nokton48, on Flickr

    Here is my homemade "Zone Board" as described and discussed in the back of "The Art of Pyro" by Gordon Hutchings.

    From the top, Zone VIII, Zone VII, Zone VI, Zone V, Zone IV, and Zone III. As I recall that was really all the info you needed to plot.

    Nice big references when you go to measure the negs.

    I will be firing this back up soon, as I have time.
    “The secret of getting ahead is getting started.”
    ― Mark Twain

  5. #15
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    Re: Need Guidance on Getting a Sensitometer

    Oren, et al, here's another reference to using a sensitometer for film testing:

    https://www.youtube.com/watch?v=VNbyShwYi6c
    Keith Pitman

  6. #16
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    Re: Need Guidance on Getting a Sensitometer

    Quote Originally Posted by Keith Pitman View Post
    Oren, et al, here's another reference to using a sensitometer for film testing...
    Excellent, thank you!

  7. #17

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    Re: Need Guidance on Getting a Densitometer

    Thanks. I just purchased the kindle edition of BTZS and will check it out for more details that will likely help fill in the cracks.


    Quote Originally Posted by Oren Grad View Post
    Thanks for that link!

    As you're figuring out what will work best for you, do take a look at "Beyond the Zone System" if you haven't already - the current edition is pricey but earlier editions are available inexpensively on AbeBooks. Phil described his procedures in detail.

  8. #18

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    Re: Need Guidance on Getting a Sensitometer

    Thanks Keith. I will watch it and see if it will help fill in some missing info for me. Have a good weekend.

    Larry

    Quote Originally Posted by Keith Pitman View Post
    Oren, et al, here's another reference to using a sensitometer for film testing:

    https://www.youtube.com/watch?v=VNbyShwYi6c

  9. #19
    Greg Davis's Avatar
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    Re: Need Guidance on Getting a Sensitometer

    That video is mine. I also have two videos following along with the Kodak Basic Sensitometry Workbook. Part 1 ( Exposing the step tablet and drawing the curves) is here: https://youtu.be/eILVzTNWnq8, Part 2 (Calculating Gamma) is here: https://youtu.be/OnhcX3x2YvU. I will get Part 3 (Contrast Index) up this weekend.

  10. #20
    ic-racer's Avatar
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    Re: Need Guidance on Getting a Sensitometer

    In addition to the information provided by Greg above, you might find these threads useful:

    https://www.photrio.com/forum/thread...e-soon.175464/
    https://www.photrio.com/forum/thread...hootout.95837/

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