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Thread: Bellows Exposure calculation

  1. #1
    smithdoor's Avatar
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    Lightbulb Bellows Exposure calculation

    If you need Bellows Exposure calculation down load with filter calculation
    Try this wheel for calculations

    Dave
    Attached Thumbnails Attached Thumbnails BellowsWheelPart3of3.pdf   BellowsWheelPart2of3.pdf   Bellows Wheel1of3.pdf  

  2. #2

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    Re: Bellows Exposure calculation

    The reciprocity timer app for iPhone does all that for you, it's really great and was developed by a LFF member

    Check it out on the App Store

    https://itunes.apple.com/us/app/reci...459691262?mt=8

    Click image for larger version. 

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  3. #3
    Steve Sherman's Avatar
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    Re: Bellows Exposure calculation

    Bellows Extension factors need not be nearly as confusing as some suggest.

    Placing a known object in the zone of critical focus and then taking a measurement on the ground glass of that object with a unique measurement devise can seem quite daunting.

    For years I've used a very simple method to calculate bellows extension compensation, and it's all in your head.

    Example, 210mm lens, also known as a 8 1/4" lens ( this measurement is @ infinity ) Convert the length of the lens ( in inches) to an F stop, i.e. 210mm = F 8, if your bellows extension is measured at 11 inches then you allow 1 stop additional exposure, F 8 to F 11 = 1 F Stop, if measured at 14" then allow 1.5 stop increase in exposure.

    210mm (8 1/4" ) lens extended to 16" is just slightly lens than 2 full F Stops. BTW, any size lens extended X 2 is life size, i.e. 6" lens extended to 12" or 10" lens extended to 20" produces a life size image on the ground glass and always dictates a 2 stop increase in exposure.

    Some may say this method is not accurate enough, for years I did product / table top photography with box specific ISO Ektachrome film and rarely missed a bellows calculation.

    Cheers


    Real photographs are born wet !

    www.PowerOfProcessTips.com

  4. #4

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    Re: Bellows Exposure calculation

    Quote Originally Posted by Steve Sherman View Post
    Bellows Extension factors need not be nearly as confusing as some suggest.

    Placing a known object in the zone of critical focus and then taking a measurement on the ground glass of that object with a unique measurement devise can seem quite daunting.

    For years I've used a very simple method to calculate bellows extension compensation, and it's all in your head.

    Example, 210mm lens, also known as a 8 1/4" lens ( this measurement is @ infinity ) Convert the length of the lens ( in inches) to an F stop, i.e. 210mm = F 8, if your bellows extension is measured at 11 inches then you allow 1 stop additional exposure, F 8 to F 11 = 1 F Stop, if measured at 14" then allow 1.5 stop increase in exposure.

    210mm (8 1/4" ) lens extended to 16" is just slightly lens than 2 full F Stops. BTW, any size lens extended X 2 is life size, i.e. 6" lens extended to 12" or 10" lens extended to 20" produces a life size image on the ground glass and always dictates a 2 stop increase in exposure.

    Some may say this method is not accurate enough, for years I did product / table top photography with box specific ISO Ektachrome film and rarely missed a bellows calculation.

    Cheers
    I'm lost, this is not at all easy, especially if you don't know how to convert mm to inches in your head... Why can't you keep it at mm's?

  5. #5

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    Re: Bellows Exposure calculation

    Of course you can; as long as you know how many stops are between f210 and f420.
    There are as many ways to learn this as there are learners.
    Smithdoor's wheel is another good way.
    As always, the best is to understand the principles and then you can understand why they all work.

  6. #6

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    Re: Bellows Exposure calculation

    Quote Originally Posted by cowanw View Post
    Of course you can; as long as you know how many stops are between f210 and f420.
    There are as many ways to learn this as there are learners.
    Smithdoor's wheel is another good way.
    As always, the best is to understand the principles and then you can understand why they all work.
    I think I'll stick to the app haha and version 2 is coming out soon with zone mapping and notes and goodies. Lol

  7. #7
    Steve Sherman's Avatar
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    Re: Bellows Exposure calculation

    Quote Originally Posted by StoneNYC View Post
    I'm lost, this is not at all easy, especially if you don't know how to convert mm to inches in your head... Why can't you keep it at mm's?
    25mm = 1 Inch Always several means to an end

    Cheers!!


    Real photographs are born wet !

    www.PowerOfProcessTips.com

  8. #8
    smithdoor's Avatar
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    Re: Bellows Exposure calculation

    1" = 25.4 mm it was round off
    here one for you 1 m is close to 1 yd+ or ( 1m = 39.37" or 3' 3.37" or 1.09 yds)

    Dave

    Quote Originally Posted by Steve Sherman View Post
    25mm = 1 Inch Always several means to an end

    Cheers!!

  9. #9
    Drew Bedo's Avatar
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    Re: Bellows Exposure calculation

    I have pre-calculted the correction for my two most used lenses, 150mm and 210mm.

    When in the field, I compose and focus, then measure the total amount of extension. For the 150 (6 inches, right) each inch beyond infinity is one third of a stop extra exposure.

    For the 210mm (8.25 inches) the correction that I use is one quarter of a stop extra exposure for each inch beyond infinity.

    To each his own: You can make this as complicated as you want. There are many threads on this topic and many methods—some with formulas (Ok: So what if the plural is "formulae).

    Try out a few ways and settle on what works for you.
    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!

  10. #10
    Kirk Gittings's Avatar
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    Re: Bellows Exposure calculation

    http://www.salzgeber.at/disc/disc.pdf

    I use this simple tool. It works fine and I don't have to use my math challenged brain.
    Thanks,
    Kirk

    at age 73:
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

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