Aug 112015

Light beams in Fossil Cave

About the site

Fossil Cave is a small cave-rated dive in Mt Gambier. It’s close to Tank Cave, close enough that there’s ongoing speculation that one day divers might be able to swim from one to the other. It’s a shallow affair but does display the crystal clear water that makes you think you’re diving through air. The cave was named after the fossil remains which were extracted for study back in the 80s.

Darkness in Fossil Cave

About the dive

There’s less light in winter but the lower angle of the sun means it comes in at a better angle for cave entrances like Fossil and Pines. On the day we had high winds and scudding clouds so the sun beams were a hit and miss affair. We started the dive at the back of the main room, lined up against the wall and practising the lighting.

About the shot

The second shot you see here was taken with no on camera light at all. As per the exercise in Weebubbie more than a year again which resulted in this shot, these are a little tricky. We started by lining things up, then turning off our dive lights. Fossils had just enough ambient light coming in from the entrance to make this a bit easier than my experience in Weebubbie. Lucas lined up a small LED torch against the triggerfish sensor for the strobe. I turned one on camera strobe onto the lowest setting and twisted it to point back behind me. Then with the lights out and the camera on bulb mode I hit the shutter.

When he saw the flash Lucas clicked the torch on to trigger the off camera strobe. And when I saw his flash, I let go of the shutter. The eventual shutter speed was around one second – the reason why this only works in the dark! I bumped the f stop higher and got closer to ensure the very dim daylight wasn’t being recorded. I love this effect of a pool of light around a diver in darkness. It’s much more closely related to what I see when I cave dive with buddies. The angle of the off camera light bouncing back towards the camera makes for interesting shadows.

With the photo under our belt we headed around the wall to see the sunlight just starting to peek through the clouds. It came and went but luckily was beaming through the water by the time we were back in the main entrance. By this point I was back to regular on camera strobe firing with a low shutter speed to catch the ambient light, and captured the top shot here as Lucas came over the top. It was mid winter in Gambier with associated freezing rain and gale force winds. From the underwater sunlight, you could almost imagine something more pleasant.

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