Dry Land Training: Focus Distance

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Finding your minimum and maximum focus distance is a critical skill in underwater macro.  This is because if you can’t focus, you can’t take pictures that you’ll like.  In supermacro, most of the the time you can’t even see your subject because the depth of focus is so thin.

I test for maximum and minimum focus distance every time I have a new camera, lens, or wet diopter.  I’ll even test combinations of these 3 to see what I like.

Given:

  • A well-lit room
  • One camera with lens
  • One housing with appropriate port
  • Series of wet diopters
  • A subject (can be a nudie replica or something as mundane as the screw on a tripod head)

Process:

  1. Mount camera and lens in housing with port.
  2. Find minimum focus distance first.
  3. Put the glass of the port up against the subject.
  4. Try to gain focus with the auto-focus–back-button or half-press on the shutter.
  5. When you have the closest focus point, measure the distance from the end of the port to the subject.
  6. Check for farthest focus point.
  7. Move the camera back from the subject while you are trying to gain focus.
  8. When you can’t focus anymore, go forward just a bit and get a focus.
  9. When you know the furthest focus point, measure the distance from the end of the port to the subject.

Tricks:

  • Put the camera in constant focus mode:
    • Panasonic: AFC
    • Canon: AI Servo
    • Nikon: AF-C (Continuous-servo AF)
  • Us manual focus to set the minimum and maximum focus distance.
  • Put the subject on a ruler so that you can easily measure the distances.
  • Try stacking wet diopters.  I sometimes use a Nauticam SMC-1 with a Saga +5.  Different diopter combinations have different focus ranges.
  • Once you have a focus lock, move the camera in and out to see how deep the focus is.  Try it with maximum and minimum aperture.

 

See you all underwater!!!

–Mike