• Nathan Litjens

Glows and echoes - trying to photograph a complex scene involving bats and glowing insects.

It's very tricky to get photos of very fast and very slow things in one image, but last night I made it happen!

The cave is well lit with predatory glow worms

Last week I was invited to a bat roost in northern NSW, Australia by Brett Vercoe. While I was there I noticed the massive amount of glow worms (Arachnocampa) at the entrance of the cave and all along the ceiling. Immediately I imagined a photo that I just had to have a go at taking.

I imagined a photo of a bat in flight with the glow worms and vegetation in the background. They didn't have to be focus, but the bat did. Also the light from the flash needed to imitate moonlight as well as possible. So, how would I go about doing this? Well, as it turns out, it's not so hard, just a little fiddly. Last night I set out to put this idea into practice.

First I set up the camera on the correct angle, inside the cave looking out. It was hard up against one wall and aimed so the left half would have the glow worms but leave enough empty space for the bats in the right half. I needed the bats to not be superimposed over the glow worms if at all possible.

Second, I set up the break beam vertically and in the spot that I wanted the bats to appear in the photos. The 24mm lens was focused on the beam itself.

Third, I set up the lighting. The primary flash was on a diffuser and aimed downward, just like the moonlight. A blue filter was added to it for a moon effect. A second flash was added much higher up, looking down as well. The break beam was connected to the flashes directly. They were set to 1/32 power.

The camera was originally set to 3 mins exposure on my intervalometer at an ISO of 1600, f/10.

Now all I had to do was await darkness and get some bats!

There is such thing as too many bats! There is a very real chance of multiple flash exposures during a three minute camera exposure!

There was quite a lot of traffic and most of my photos had multiple flash exposures as many bats triggered the flashes before the exposure was done. Eventually I had to limit it to 1 minute and wait until midnight when traffic was low enough and only one bat at a time broke the beam!

An eastern bentwing (Miniopterus orianae oceanensis) banks hard on the way back into the cave. A spider is hanging at the top margin of the image.

The glow worms showed up well, though you won't see the true density of them in the pictures. There would have been about 150 per square metre! However only the larger ones show up well in the images, but that's fine by me. The blue filter didn't work well enough so I had to change the colour temperature in Lightroom to make it look the way I originally wanted. Other than that, I made only the most trivial adjustments.

Eastern horseshoe bats (Rhinolophus megaphyllus) were the most numerous in the cave at this time of year, this one was well lit by the flashes.

Sometimes double exposures worked well, simply because these two bats were in the exact position I wanted them in.

I'm very happy with the images and they are now uploaded to the Zenfolio gallery. Click on "Conservation Images" on the top right and go to the Mammals gallery.

Would you like to do a bat photography workshop in the field one day? Let me know in the comments!

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