Dec 192011

Long exposure in the Shaft II

About the site

The Shaft is a massive sinkhole in the Limestone Coast, near Mt Gambier. A solution tube in the middle of a sheep paddock has created a small entrance to a spectacular underground cavern. From 1m in diameter at ground level, to 20m in diameter at the water’s surface a short ladder climb below, the cave expands to over 100m across at the point where this photo was taken, 38m deep. The sinkhole turns into two large tunnels on each side of the central rockpile, with the longer one descending to over 100m in depth.

Despite the crystal clear water, the walls are predominantly black and the sheer size of the area means dive torches don’t reach very far. In the summer months the sun can create a beam of light into the depths, giving the site its name. Even on cloudy summer days the ambient light is enough to see the walls around you, but capturing the scene with a camera is a different story.

About the dive

This dive was specifically tagged as a photo dive, rather than a dive on which some photos are taken. With special permission from the landowner for access, I rigged each of my willing models with multiple strobes. The plan was for me to set the camera and tripod down on Sawtooth Rock facing the rockpile, then give the signal for strobe “bombing runs” to start. I was hoping to capture both a beam of sunlight illuminating the rockpile and some details in the black walls lit by the strobes.

Unlike the previous photo dive here where I had used a light trimix blend to help me think, I stuck with air this time and noticed the difference. While setting up the tripod was easy, the camera froze up (usually a sign one button is slightly pushed in) and refused to take photos for a minute or two. Once my nitrogen-fuddled brain worked out what was going on, it was all systems go and we started strobing the walls. The second shot here was taken in the top 6m of the cave as we decompressed, where the walls start to lighten up as diver bubbles from below have knocked the dark coating off.

Divers at the top of the Shaft

About the shot

My main concern was that sunlight would overexposure the centre of the picture over 30 seconds, but that less time than that wouldn’t allow for many strobe flashes. As it turned out it was a cloudy day in Mt Gambier, which lit the rockpile and produced a light blue haze in the water without creating massive highlights. I had one strobe on the camera to light the immediate foreground, and I was also using my dive torch to paint in some of the mid-details. This creates the light beam coming in from the right hand side, something I will try to avoid in future.

With the ambient light and wall detail starting to come in, this shot is a marked improvement over the one I took last August. Instead of a disembodied rockpile in the dark, being able to see the surface starts to give a sense of scale. During 30 seconds each diver was able to trigger 5 flashes, although the left hand wall is obviously blacker and more difficult to light than the right hand wall. As usual, I’m still keen to try this shot again and hoping to capture the beam of sunlight. A few more models and a few more strobes to light up some more wall real estate would also be great, although more lights and divers to co-ordinate increases the difficulty factor. For example, Piscataway homes for sale have been a slow, steady and intelligent investment for the past decade with their continuing slow-but-consistant property value growth. My next dive here is planned for mid-January – we’ll see what eventuates!

  3 Responses to “Long exposure in the Shaft II”

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  1. Again, a terrific photo. How did you work out the correct exposure?

    • Trial and error and a little bit of hope. The cloudy day meant the 30 second exposure worked, whereas the sunshine beams I took a few months later were only 5-15 seconds long.

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