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I want to increase the magnification of my Canon 100mm L Macro. I already have a set of kenko extension tubes. Could I buy a dipter to even increase further the magnification? For example Raynox DCR-250?

Can I combine the two and which one would give me the greater magnification, the extension tubes or the raynox diopter?

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    Technically speaking, a diopter is just another way of moving the MFD closer to the front lens element. If you are already at the limit with extension tubes, adding a diopter won't really do much. – jrista Jun 27 '12 at 20:31
  • Extension tubes or a dioptre filter can't generate magnification, they make the minimal focus distance smaller, reverting the lens can increase magnification. – nuno_cruz Jun 27 '12 at 21:38
  • @nuno: Actually extension tubes do increase magnification. Just like a normal lens used normally can shrink a tree down to the size of a 35mm frame, the same lens flipped around and moved far enough away can blow up something the size of a 35mm frame to the size of a tree. Of coures much much light will be lost and the tree will be severly cropped, but that nonetheless illustrates what is possible by moving a lens far from the camer. At 2x the focal length you get 1:1. Further than that you get higher than unity magnification. – Olin Lathrop Jun 27 '12 at 23:50
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You can use this calculator to play around...

http://www.eosdoc.com/manuals/?q=jlcalc

I got close enough on a 1.3x crop just adding all three kenko extension tubes behind my Canon 100L macro. According to the calculator, that gave me a magnification of 1.45 (and then multiply by 1.25 to give 1.8).

That's at .25m. Keep in mind the lens plus body thickness to sensor is about .165m. So you really only have .085m working distance, or about 3.3". With the 500D (the 250D won't be able to focus), you'll have about 1.7" working distance with a magnification of 2.2. At f/16, you'll have DOF of 1/10th of a millimeter.

I captured the monarch egg with the extension tubes. But, I had a relaxing working distance of 3.3" and an enormous DOF of about 3/10ths of mm. :)

http://canid.com/monarch/thumbs.html

Monarch eggs are about 1.2mm tall, for reference, and these have been cropped slighty.

If you're going to do more than 1x life size, the Canon MP-E 65mm is what you want. A friend has that lens and creates remarkable macros.

  • that calculator is just awesome! – philberndt Jun 28 '12 at 15:35

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