Macro Len Combination Questions

Discussion in 'Macro Photography' started by RalphP13, Feb 19, 2010.

  1. RalphP13

    RalphP13 TPF Noob!

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    I know I can combine a macro lenses with teleconverters and extension tubes however I'm trying to get a grip on how this affects things.

    Putting a 2x teleconverter on a 105 mm lens gives me a 210 mm focal length, however, does it affect my magnification (i.e. change my 1:1)?

    Also, I think I understand if I put an extension tube on a macro lens I increased my magnification. Therefore if I put a 105 mm extension tube (105 mm for the sake of discussion) I end up with a 2:1 magnification, right? Does my focal length change or stay at 105 mm?

    Does this also mean that extension tubes of the same size would give more magnification to a shorter, 60mm, macro lens than a 105 mm macro lens? I was under the impression that extension tubes work better on longer focal lengths or is that just because of the working distance?


    Thanks, Ralph
     
  2. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Adding a teleconverter will both increase you focal length and magnification factor by the multiplier of the lens.

    So a 1.4TC:
    105mm 1:1 macro lens becomes a 147mm 1.4:1 macro lens

    And a 2*TC
    105mm 1:1 macro lens becomes a 210mm 2:1 macro lens.

    Adding tube length is also another way and for this the rough maths is that the length of tube added is directly linked to the focal length of the lens. The longer the lens the more tube length you need to increase the magnification factor. So on a 50mm lens you only need 50mm of tubes - whilst the same magnification boost on a 105mm lens would need 105mm worth of tubes*. Thus the shorter lenses work better overall with tubes.

    For longer lenses I would recomend looking at the Raynox Diopters (macro filters) which work similar to tubes, but are a lens element instead of empty tubes. The DCR250 is a good budget starting point however there are also more powerfull setups which offer combinations of macro diopters which you can stack together to get even more magnification.


    *this is rough maths answers there is a more complex formula that gives the correct actual amount
     
  3. RalphP13

    RalphP13 TPF Noob!

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    Thank you very much Overread!!

    Your information is much appreciated. :thumbup:

    I was aware of the diopters (macro filters, close-up filters), but I figured I would have less of a chance of image degradation with empty space (extension tubes) than putting glass in front of the lens. I'll take a look at the Raynox diopters.

    Do you or anyone else know of additional high-quality diopters to consider?

    Thanks, Ralph
     
  4. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    It's a common belief that no glass means no loss of image quality - however whilst there is no glass the lens is being moved and thus the light is no longer hitting the sensor at it optimum - thus there is some image degradation even with tubes. Most of the time though its very small and you won't really notice it at all.

    The Raynox diopters - whilst using glass -are also surprisingly high grade products for their low price. John Hallmen Flickr: johnhallmen's Photostream does a lot of work with many different macro setups and much of his work is going well beyond the 1:1 magnification of a regular macro lens and he can't sing high enough with praise of the Raynox diopters. Infact in a recent test he did a Raynox Diopter plus another lens (and a few other bits) beat the Canon MPE 65mm macro in image quality. So the Raynox are certainly worth considering.

    Myself I have both tubes and a Raynox DCR250 and I find the diopter gets a lot more use. Its quick to put on and take off (unlike tubes which take time) and is light and easy to pack.

    Other good diopters would be the Canon 500D (yes they use the same name for a diopter as a camera body) and also I belive Nikon make a good diopter as well.
     

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