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Thread: bellows factor app

  1. #1

    Join Date
    Aug 2006
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    bellows factor app

    hi all
    I don't suppose there is an app for bellows extension?
    thanks

  2. #2

    Join Date
    Sep 2003
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    Massachusetts USA
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    Re: bellows factor app

    See the Reciprocity Timer app for iPhone.

    It combines bellows extension, reciprocity compensation and filter factors for a wide variety of films.

    I've used it many times.

  3. #3

    Join Date
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    Re: bellows factor app

    Quote Originally Posted by dave4242 View Post
    hi all
    I don't suppose there is an app for bellows extension?
    thanks
    Do you really need it?

    Life size open up 2 stops, half life size open 1 stop, twice life size open 4 stops, quarter life size open up Ĺ stop.

    It is a progression, most donít need an app. Just 2 rulers, one at the scene and one at the gg.

  4. #4

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    Aug 2006
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    Re: bellows factor app

    I was just curious.. thanks!

  5. #5
    Mark Sawyer's Avatar
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    Stuck inside of Tucson with the Eastern Seaboard Blues again...
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    Re: bellows factor app

    The f/stop is just a ratio, focal length (bellows extension) divided by aperture. You're standing there with a ruler or tape measure in your hand anyways, why not just figure out the real f/stop and be done with it?
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  6. #6

    Join Date
    Dec 2014
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    76

    Re: bellows factor app

    Take a 10 inch lens for this example. If the bellows is less than 10 inches (from the nodal of the lens to the film) then you do not need to worry about bellows factor, it is factor of 1. Once the bellows is longer then 10 inches, say it's 14 inches, then divide 14 into 10 to get 1.4, square 1.4 to get a factor of 2, double the exposure time. A bellows at twice the length of the lens, 20/10 = 2, square 2, will give a factor of 4. You can also use a metric measurement, it does not mater.

    If the bellows is shorter than the focal length of the lens, expose without compensation.

    at 125% extension add 1/2 stop to the light meter reading.
    at 140% extension add 1 stop
    at 175% extension add 2 stops
    at 200% extension add 4 stops

  7. #7

    Join Date
    Feb 2011
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    Rockville, MD
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    28

    Re: bellows factor app

    Just in case anyone’s curious, there actually is an app for Android (I don’t know if there’s an equivalent iPhone app) called Bellows Factor (www.rdq.cz).

    Cheers, Allan

  8. #8
    Drew Bedo's Avatar
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    Oct 2006
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    Houston Texas
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    Re: bellows factor app

    My favorite lens in the field is marked 150mm (or 6 inches). Having worked it out ahead of time, for every inch of bellows extension beyond 6 inches I open up 1/3 stop.

    With my 210mm (8.25 inches); for every inch of bellows extension beyond 8 inches, I open up 1/4 stop.

    These approximations have been close enough for work outdoors.

    I can do this in the late afternoon while standing in wind blown sleet (but I don't like it)
    Drew Bedo
    http://www.artsyhome.com/author/drew-bedo




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

  9. #9

    Re: bellows factor app

    My favorite app is a tape measure
    And it never needs charging

  10. #10

    Join Date
    Nov 2014
    Posts
    11

    Re: bellows factor app

    Iím with Peter on this one. I made a simple string with segments that I hang on the rear of the camera. When stretched out to measure the bellows, it tells me how many 1/3 stops that I need to factor in.
    Bellows factor becomes an issue at the first black section and then 1/3 more for each additional section. You would have to make one for each lens you have or just use a tape measure and do the math.


    Here you can see the lens intersects with the string at about the 3rd segment. So I would add 1 full stop (Three 1/3 clicks)


    It even doubles as a solution to them sagging bellows with a well placed clip


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