Trying to understand macro and lenses

Discussion in 'Photography Beginners' Forum' started by scottsmac, Oct 13, 2008.

  1. scottsmac

    scottsmac TPF Noob!

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    I like getting pics of bugs and other small things with my 18-55mm that has a minimal focal distance of .25m and I'm trying to figure out what size image this is making on the sensor in an effort to compare this to other proper "macro" lenses that are able to produce a 1:1 sized image or even a 5:1.

    How can I figure out the image size with only the focal length and closest focal distance? Or do I need more information then this?

    Thanks for the info
     
  2. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    Measure the graduations on a ruler. You know how large your sensor is, (It will be in your camera's manual), so simply set your lens to it's minimum focusing distance and and the move the ruler until it's in sharp focus (Ensuring it remains square to the lens axis). APS-C size sensors (The majority of DSLRs) are approximately 23x15 mm, so if at minimum focusing distance you can see 46mm on the ruler, you know you're getting 1:2 or 1/2 true macro. Bear in mind, this isn't exact; your viewfinder may not show 100%, but it will serve as a guideline.

    I'm not aware of any lens that can produce a magnification of 5:1; that's verging on microscope territory. A few macro lenses can do 2:1, and if you use a macro lens plus extension tubes or close-up lenses, you might get something like that, but your optical quality isn't going to be very good.
     
  3. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Canon MPE 65mm - capable of zooming from 1:1 macro to 5:1 - only lens in production that can (as far as I know)
    and on my wishlist of lenses!
    Its also a macro only lens - no infinite focus - and reportedly one of the hardest lenses to master the use of
     
  4. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    Oh. A Canon. Sorry. I thought we were talking real gear!





    :p


    Cool, I didn't know such a beast existed. That is a special-purpose lens. What does it sell for?
     
  5. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    UK price around £600 and under (currently £588 on amazon) but you do need good light support with it - and the canon positional macro flash unit is often used since you can have the lights turn on to provide extra light for focusing (Canon MT-24EX), very important when dealing with the greater than 1:1 macro work (flash retails at around the same price - so a good £1100ish for the pair)
     

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