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Thread: Bellow extension expsosure help!

  1. #11

    Join Date
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    Pittsfield, MA
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    Re: Bellow extension expsosure help!

    B&H has the new one here, mine doesn't have the rainbow colors,

    http://www.bhphotovideo.com/c/produc...k_for_4x5.html

  2. #12

    Re: Bellow extension expsosure help!

    Quote Originally Posted by davidp View Post
    but would I need to do this with my normal Sinar F2 bellows on the rail or does it only count when I add a second rail/bellows?
    Depends on the magnification. And the magnification you'll get from a certain extension/bellows depends on the lens. With a 75mm lens at 150mm extension you'd be at life size and need to correct for extension. While with a 150mm lens and the same extension you'd be focused on infinity. So, don't think of extension as an absolute quantity independent of focal length.

  3. #13

    Re: Bellow extension expsosure help!

    I use a 210mm if that helps?

  4. #14
    SF Bay Area 94303
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    Re: Bellow extension expsosure help!

    Gosh folks make this hard. If the image is 1:1 you need two more stops and your lens will be pulled out twice as far as it is at infinity. For a 210mm it will be pulled out 210mm further than infinity.

    At half real life size you need one f stop more and your lens will be pulled out about 105 mm past infinity. You can estimate the intermediate values. Don't forget about reciprocity failure. K

  5. #15

    Re: Bellow extension expsosure help!

    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?

  6. #16
    All metric sizes to 24x30 Ole Tjugen's Avatar
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    Re: Bellow extension expsosure help!

    Bellows extension exposure compensation depends not on the total extension of the bellows, but on the relationship between focal length and bellows extension. Which is to say, reproduction ratio. Or magnification, if you like.

    That's why all the answers here are correct but do not answer your original question: You've asked the wrong question.

  7. #17

    Re: Bellow extension expsosure help!

    "Bellows on my Sinar are fully stretched out" is a bit vague for people who don't own a Sinar. That's why all the answers ask you to consider the actual lengths of te extension and your focal length. How long is "fully stretched out"? If you measure that and know your focal length (210) the you have your answer. But for full body portraits, the short answer is that you don't need to worry about compensation.

    -A

  8. #18
    Drew Bedo's Avatar
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    Oct 2006
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    Re: Bellow extension expsosure help!

    If the Film plane to lens node distance equals the focal length of the lens, the exposure compensation is 2 stops. For my 150mm lense, this amounts to one third of a stop for each 25mm (each inch) of extension. For my 210mm its about a quarteer stop for every 25mm/inch of extension. This is easy to measure and easy to apply. Just figure it out for the focal lengths you use.
    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!

  9. #19

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    Re: Bellow extension expsosure help!

    Drew, didn't you mean to say "twice the f.l. of the lens"?

  10. #20

    Re: Bellow extension expsosure help!

    Jason Brunner has a bellows factor
    compensator thingie you can download here:

    http://www.jasonbrunner.com/files/jbbellows.pdf

    and a video demonstration on how to use it posted here:

    http://www.youtube.com/watch?v=vwfRA...eature=related

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