Extensions for Macro

Discussion in 'Beyond the Basics' started by smoke665, Feb 13, 2018.

  1. smoke665

    smoke665 TPF Supporters Supporting Member

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    Manual only extension tubes are quite a bit cheaper than auto. For someone who only occasionally does macro is it really worth the added cost for the auto?


     
  2. adamhiram

    adamhiram No longer a newbie, moving up!

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    You probably won't use autofocus at all, but electronic aperture control on "gelded" lenses is a must, unless you want to shoot only at the smallest aperture (I think that's what Nikon defaults to, I believe Canon is the opposite), or get an extra adaptor that adds an aperture ring. If you're already shooting with fully manual lenses, it shouldn't matter. I opted for the Kenko extension tube set that has electrical contacts, which wasn't too expensive.
     
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  3. smoke665

    smoke665 TPF Supporters Supporting Member

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    Well Duh, forgot about aperture, that takes my new glass out of the mix. Think I may still gave a couple old school models with the aperture ring, but for the difference in price I think you answered my question.
     
  4. weepete

    weepete TPF Supporters Supporting Member

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    With Canon bodies you can use the depth of field preview button to close the aperture down to your desired setting and keeping the DOF preview button pressed remove the lens from the body. The aperture should then stay at the desired setting. I don't know if that works for other brands though.
     
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  5. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    For $125 or so US for a set of Kenkos, it's an inexpensive way to get into macro.
     
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  6. Boutch

    Boutch TPF Noob!

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    Is it not truly ‘macro’ when you use these tubes? I’m under the impression that it brings your minimum focus distance right in, but it results in a far lower quality image than true macro
     
  7. Derrel

    Derrel Mr. Rain Cloud

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    Kenko AF extension tubes are _well,well,well_ worth the money. You maintain autofocus; maintain automatic diaphragm control, maintain TTL flash capability, maintain automatic exposure, maintain manual exposure, and maintain EXIF reporting. All of the above things make it well worth the money to purchase CPU-contact-equipped extension tubes.

    For most lenses, a 12mm and a 20mm extension tube make the two most-useful tubes; the 36mm tube is often fairly useless. Be aware that with shorter lenses, adding extension can bring the focusing distances actually _inside the lens barrel itself_, which kinda sucks! With something like say a 24-70mm zoom lens, at the shorter end, even a 12mm extension tube can bring the focusing range _inside_ the lens itself at the shorter focal lengths! What a PITA! At the longer end, like rom 70mm down to say 40mm (approximate figures, from memory), the 12mm tube will be usable.

    Manual, no-contact tubes are a huge PITA with modern d-slr cameras and with some lenses!
     
  8. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    They cannot degrade the image any as there's no glass in extension tubes. If you get poor image quality, it's due to the poor lens you are using, not the tubes.
     
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  9. weepete

    weepete TPF Supporters Supporting Member

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    Yup, it will also magnify any existing issues. So while extension tubes won't add any issues like a sub par diopter would they can cause a lens to seem poorer as existing issues will be more apparent. Still, some pretty cool results can be acheived even using cheap lenses.
     
  10. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Within photography there isn't a strict term for macro as such (nikon doesn't even call their macro lenses macro and instead calls them micro). This is partly gotten away by the fact that the majority of photography is artistic rather than scientific and when science and accurate measuring is required aides (eg a ruler) are often used within the photography for scale rather than calculations based off photos.
    However the generally agreed upon definition by the vast majority of photographers, books and references is that

    (true) macro is when the size of the subject reflected on the sensor by the lens is equal to the size of the subject in real life. Written as 1:1 ratio.

    Now extension tubes work by reducing both minimum and maximum focusing distances on a lens they are fitted to. They are used for two primary functions. First to get macro or close up photography shots; the second is to gives a closer working distance for some super-telephoto lenses where the min focusing distance of the lens might be several feet and where a setup (eg hide trained on a bird feeder) might bring subjects far closer than the minimum distance.

    The rough maths for extension tubes is:
    (length of extension tubes in mm - divided by - Focal length of the lens) + magnification of the lens

    Baring in mind that the magnification of the lens can change through its zoom/focusing range and that in many non-macro lenses this value is low enough that, in most casual uses of the calculation, its often left off so people just focus on the division.


    From this rough maths and definition you can see that a 50mm lens and around 50mm or more of extension tubes (eg a full set of kenkos) would give you a lens that achieves slightly more than 1:1 magnification; thus very comfortably into the common definition of true macro (with regard to photography)






    As said above, extension tubes lack optics so they won't directly degrade image performance in that regard; but moving the lens further does magnify the image generated and thus will highlight any weakness in the lens. That said many times the lower image quality is the result of imperfect method by the photographer. Often not using lighting well or not accounting for the dramatic reduction in depth of field that macro brings with it.
     
    Last edited: Feb 20, 2018
  11. Boutch

    Boutch TPF Noob!

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    Ah, very nice. Thanks heaps for going to the time to write that up, it’s very informative.
     
  12. smoke665

    smoke665 TPF Supporters Supporting Member

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    @Derrel so if I understand correctly what you and @Overread are saying, the use of extension tubes on a lens like my Pentax 35 Ltd macro, wouldn't really be of significant benefit as it's already 1;1 and has a minimum focus distance of just under 6 inches?
     

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