Tips for photographing bioluminescent plankton

The other night I got to witness bioluminescent plankton doing its stuff. It truly was an amazing sight. It turned waves and ripples into a shimmering electric blue, and if you looked closely at the rocks or the shore, you could see tiny sapphire pinpricks glowing away.

It was amazing.

But it was also challenging to photograph.

I do a lot of night photography so I knew I’d need a wide aperture (I went for F2.8), a show shutter speed (I was working between 8 seconds and 20 seconds) and an ISO high enough to catch the plankton glow but low enough not to give me noise problems (the Canon 5D MkIII was happy at around 3200 to 4000 ISO).

However, trouble came when it came to focusing. Normally I shoot wide at night, but I wanted to get in close to the action with this so I shot with a Canon 70 – 200mm lens, and so I didn’t just have the option to set the focus on infinity and fire away. I had to be more specific, but that isn’t easy when you’re trying to focus in the dark on tiny glowing things.

I took three different approaches to focusing:

  1. Just eyeball the distance, set the focus on the lens to that distance, and hope for the best. This worked pretty well.
  2. Shine a light on an object and auto focus on it. Again, this worked pretty well.
  3. Manually focus on the plankton. This was trickier to do as the viewfinder and live view was dim.

Oh, and as always, I shot a lot, and checked the image on the live view to see what I got. I knew I might not get a chance to see this again, so I wanted to make sure that I got the shots I wanted in the can before calling it a night.

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