extension tubes

Discussion in 'Beyond the Basics' started by panocho, Apr 12, 2005.

  1. panocho

    panocho TPF Noob!

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    I want to start doing some macro photography beyond the restrictive limits I have now -this means beyond some zoom lenses with macro and close-up filters, all of which give ratios of at most 1:2.

    I would like to reach, at least, 1:1, and then, if affordable, 2:1 would be also great. But 1:1 is my main target now.

    I think that extension tubes is the best option, in terms of cost and results. But I don't know much about extension tubes. I mean, of all the extensions available, how do they get which ratios, etc

    Do you know of some place where this is explained a bit (books, web)?

    And also, do you have any other recommendation?

    My plan is to get the tubes/s for my Nikons. Wish I could just buy a micro lens!
     
  2. Digital Matt

    Digital Matt alter ego: Analog Matt

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    Extension tubes macro ratio can be figured out by tube/focal length.

    Ie. 65mm of tubes on a 50mm is 65/50, or 1.3:1.

    2:1 is pretty tough to get with extension tubes. Bellows would be a better option, but keep in mind the amount of light you are losing, the further away you get your lens from the film plane.

    I use a 50mm and Kenko extension tubes, and I've been very satisfied with the results.

    I found these tubes, which are cheaper than Kenko.

    http://www.adorama.com/MCAETNKAF.html
     
  3. photobug

    photobug TPF Noob!

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    Buy a reversing ring (they're about $15 or so) and stick that on the cheapest extension tubes you can find. You won't need anything expensive since the lense is mounted backward & you focus by moving the camera anyway.

    Depending on which lens you use (wider means more mag) and how many extension tubes you use you can get some pretty large mag factors.

    Just the reversing rign itself will go >1:1 with a 50mm, but the working distance is less than an inch.
     
  4. ferny

    ferny TPF Noob!

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    As Matt said, you work out your magnification by dividing the length of extension by the length of the lens. So a 50mm lens with a 50mm extension tube gives you 1:1 (50/50=1). Everything you take a picture of will be its real size on the negative.
    Increase that extension to 100mm and you've got a ratio of 2:1 (100/50=2). Everything on the negative will be twice the size it is in real life, it will be doubled.

    I'd say tubes are your best bet if you know you want to get into macro. They're just hollow tubes so don't affect image quality. You will have to increase your exposure times.

    Bellows are another option as Matt said. But, they're heavy and limiting. You get infinite adjustment with them. With tubes you get sets of specific lengths and you play around with what you have. Say you have a 10mm, a 30mm and 50mm set, you can only play with the combinations of those numbers. With a set of bellows (just using a basic example) that give you 10mm to 90mm adjustment you can pick any extension length you like. 32.95mm if you wanted. But they're only any good in a studio. They're too heavy to take out with you and they're not as robust as a set of tubes. Plus, with tubes you can keep adding and adding sets together if you wish. With bellows you're stuck with the greatest extension it was built with. Unless you add a tube to it...
     
  5. panocho

    panocho TPF Noob!

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    Thanks for the suggestions.
    I had already thought on a reversing ring as well, but I believe that extension tubes give you more possibilities, that is, different magnification ratios to play with.

    But it is a great idea that of having a reversing ring with a extension tube, so I'll probably go for the two things. The rings are definitely cheap, and that's always a point! Besides, they are excellent to bring with anywhere anytime.

    Anyway, extension tubes have definitely been decided. Now let's see what ebay can get me...
     
  6. DocFrankenstein

    DocFrankenstein Clinically Insane?

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    Extension tubes work best with the telephotos. :)
     
  7. tdshepard

    tdshepard TPF Noob!

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    There is still one more low-cost option to consider, namely, using a close-up lens, the kind that comes mounted in a threaded filter ring. The advantage with this method is no exposure reduction.

    A real macro lens will likely get you the best image quality though, these lenses are optimized to produce sharp images at close focusing distances. Unless you are using a very expensive, specially designed aspherical lens, you cannot eliminate spherical aberation at both short and long focussing distances.
     

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