Macros and Diopters

Closeup of zinnia

For my insect photography, I’ve been reading a lot of books and web pages about closeup photography. They usually suggest three things:

  • Diopters, a.k.a closeup lenses
  • Macro lenses
  • Extension tubes

I haven’t tried extension tubes yet, but I did buy myself a cheap set of macro and closeup lenses. However, I discovered that the directions were distinctly lacking. Furthermore, none of the books and web pages I consulted explained what these did or how to use them in words I could understand. So today I ran a few experiments to figure out just what they did and how to use them. Since flying insects in the park aren’t exactly a reproducible test case, I set up my tripod and took some pictures of a flower on my dining room table with different lenses. Here’s what I figured out:

  • A macro lens is a magnifying glass. Put one on your camera and you’ll get an image that’s twice (or three times or four times) as large, but you’ll only see half (or a third or a fourth) of the object.
  • A closeup lens (diopter) does not change the size of the image. Putting a closeup lens on your camera without changing anything else (zoom or position) has no effect on the image. However, it does enable you to stand further back and use a higher zoom. For example, if I’m 20 centimeters away, my camera can only zoom in to maybe 2X. If I put a diopter on the front, then the camera, staying at the same position, can now zoom in to 4X-6X. This means I can stay where I am instead of moving in closer to the object I want to shoot. This is important if you’d rather be holding your camera a meter away from a wasp nest than five centimeters. In other words, a closeup lens doesn’t change what you see (unlike a macro lens). It just lets you stand further back and still get the shot.

Next step is figuring out exposures and histograms.

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