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Thread: Bellow extension expsosure help!

  1. #31
    C. D. Keth's Avatar
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    Re: Bellow extension expsosure help!

    Here's an example of what I do, as I explained above. This is the list for a 10" commercial ektar on my kodak 2D (so my list tops out at the 30" of extension the camera is capable of):

    285mm 1/3 stop
    320mm 2/3 stop
    360mm 1 stop
    403mm 1 1/3 stop
    452mm 1 2/3 stop
    508mm 2 stops
    570mm 2 1/3 stops
    640mm 2 2/3 stops
    720mm 3 stops

    Those are the numbers that result in exactly those f/stop corrections. Anything in between can be interpolated and be plenty accurate for negative or for chromes. I print it about an inch by an inch-and-a-half and tape it to my lensboard.
    -Chris

  2. #32

    Re: Bellow extension expsosure help!

    Quote Originally Posted by Gary L. Quay View Post
    Steve Simmons wrote a very simple formula that I use. Every one half of the focal lenght of the lens requires 1 extra stop of light. So, when my 12" lens is at 18", I increase exposure by 1 stop. I can do the math in my head. For fine tuned studio work I use the Quick Disc.

    http://www.salzgeber.at/disc/index.html

    --Gary

    this is thte method i use. very easy to calculate exposure compensation (except for the tele lenses where i measure the film plane-lens distance and use that instead of the focal length)

  3. #33
    kev curry's Avatar
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    Re: Bellow extension expsosure help!

    Quote Originally Posted by Gary L. Quay View Post
    Steve Simmons wrote a very simple formula that I use. Every one half of the focal lenght of the lens requires 1 extra stop of light. So, when my 12" lens is at 18", I increase exposure by 1 stop. I can do the math in my head. For fine tuned studio work I use the Quick Disc.

    http://www.salzgeber.at/disc/index.html

    --Gary
    Yes... same for me. Steve's method is perfectly simple to work with even under pressure. For every 25% extra bellows extension over any given focal length add 1/2 stop. As someone suggested, sewing a cloth measuring tape to the edge of the dark cloth for measuring the bellows extension is a fabulous idea.

  4. #34

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    Re: Bellow extension expsosure help!

    Quote Originally Posted by davidp View Post
    ok? I'm not really planning to do any macro work (yet) but was just wondering if I need to apply any bellow extension exposures if my bellows on my sinar F2 are fully stretched out? I usually focus on full body portraits but I was just wondering if it applies or it isn't really that necessary, the bellows wont be going to far over the rail or anything. Is there a certain point where i will say "Woah! I need to use bellow extension exposure??" like, more than half way up the rail or something?
    Yes I think you will sometimes. I had a Sinar F some years back. Fact is only you on the day can tell for shure. You need to know how to work it out to know if you need to make the adjustment. It's the inverse square law you are dealing with, double the distance quarter the light. There are lots of ways of working out the adjustment. Find one you can relate to.

    Kevin

  5. #35

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    Thumbs up Re: Bellow extension expsosure help!

    Quote Originally Posted by Noeyedear View Post
    Yes I think you will sometimes. I had a Sinar F some years back. Fact is only you on the day can tell for shure. You need to know how to work it out to know if you need to make the adjustment. It's the inverse square law you are dealing with, double the distance quarter the light. There are lots of ways of working out the adjustment. Find one you can relate to.

    Kevin
    Just to add. Knowing how to do this is not an option with LF photography neither is it anything to be frightened of. General infinity work you will not need to work anything out, I doubt you will always be wanting to shoot at infinity. It will be to limiting not knowing wether you can shoot closer subjects for fear of under exposure.

    Kevin.

  6. #36
    Drew Bedo's Avatar
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    Re: Bellow extension expsosure help!

    When focused at infinity, the bellows extension and the lens focal length will be the same. For my 4x5 camera with 150mm lense, this is 150mm or 6 inches. To focus closer you must extend the bellows beyond one focal length. When this extension is twice the focal length of the lense (300mm or 12" in my example) the exposure compensation is two stops....Slow down by two shutter speeds or open up by two stops. If the extension is only 1.5
    times the lens focal length (225mm or 9"), the compensation is one stop (slow down by one shutter speed or open up one stop).

    Working it down this way; for my 150mm lense, every 25mm or each inch beyond infinity is one third of a stop additional exposure. For my 210mm lens, this is one quarter stop addityional for each 25mm/1" increment.

    That is as much math as I do. I use a small tape to actually measure the distance between the front of the lens board and the ground glass. It only takes a second to do. Its easy; one inch equals one 3rd stop for the 150mm or one 4th stop for the 210.

    Cheers,
    Drew Bedo
    www.quietlightphoto.com
    http://www.artsyhome.com/author/drew-bedo




    There are only three types of mounting flanges; too big, too small and wrong thread!

  7. #37

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    Re: Bellow extension expsosure help!

    My thanks to Geoff Bowker for his spreadsheet! Very nice even in an iPHONE app era. Copied and adjusted for my lenses and way of shooting (1/3 F-Stop adjustments).
    Last edited by roscoetuff-Skip Mersereau; 20-Feb-2021 at 09:09.

  8. #38

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    Re: Bellow extension expsosure help!

    Quote Originally Posted by Anupam View Post
    I have often wondered why people prefer this (just to myself, not saying that it won't work for you). Not only can this be tricky or impossible with certain subjects, putting the thing there and then measuring the image on the GG and looking up a table seems very tedious to me. Much more so than a little division and multiplication on a cell phone. It's not like it's really advanced math or a complex formula. But to each his own .
    There is no need to look up a table with this simple device. I used to make them for my LF students.

  9. #39
    Drew Bedo's Avatar
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    Re: Bellow extension expsosure help!

    Shure, spreadsheets and apps are nice to use in a studio setting i guess.

    I have tried to streamline or simplify my workflow in this so that it can be done without much deep-thought-with-squinting, or fumbling around with stuff (notebooks, iPhone) while my wife honks the car horn to let me know we are late for dinner with her mother just as the light is right . . . with a nice cloud and a bird . . .etc.

    Some things just can't be eliminated from the creative workflow.
    Drew Bedo
    www.quietlightphoto.com
    http://www.artsyhome.com/author/drew-bedo




    There are only three types of mounting flanges; too big, too small and wrong thread!

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