Alkahest my heroes have always died at the end

January 28, 2008

Macro photography

Filed under: Photography — cec @ 9:34 pm

I was talking to hunter last Friday about macro photography and a great, relatively inexpensive, device to take macro pictures with almost any lens.  Essentially, the ability of a lens to focus on a close object is related to the focal length and the distance between the inflection point of the lens (point inside the lens where the image flips) and the film plane.  It’s something of a funny relationship for modern lenses with multiple internal pieces of glass.  However, the important thing to remember is that your ability to close focus depends on those two factors.

So, the great little device to help with macro photography is an extension tube.  It has no glass, all it does is to increase the distance between the lens’s inflection point and the film.  Assuming that the focal length is constant, you can focus more closely on the subject.

For example, consider the picture below:


That’s about as close as my 18-135mm lens can focus on that quarter.   If I attach a 25mm extension tube, I can get as close as:


I could probably get a little closer, but only if I put the subject inside the lens!

There are some down sides.  The biggest is that my flash can’t actually reach the object – the lens is in the way!  What I need is either additional lighting or better yet a ring flash that sits around the end of the lens to light the object.  Adorama seems to make one for about $140.  I might check that out.


  1. The best way to get around the flash problem for still objects is to simply extend the exposure time to allow sufficient light into the camera. Of course you’ll need a tripod but have the added advantage of natural-looking light.

    Comment by Adam — February 3, 2008 @ 4:14 am

  2. agreed and that’s my usual approach, particularly for nature photography. but since this was more of a quick shot in my office with no tripod in sight… 🙂

    Comment by cec — February 3, 2008 @ 10:36 pm

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