Aug 152011

Cogwheel on the Sir William McPherson wreck

About the site

The Sir William McPherson was a transport ship originally built in 1912, and scuttled in 1949 in an area now known the Ships Graveyard. She lies in about 55m, and this was my first dive on her.

There are a large number of wrecks accessible from Portsea, Sorrento and Torquay. Prior to 1935, unwanted or damaged ships were stripped of their valuables and towed to outside the 3 mile Port of Melbourne limit before being sunk. The Great Depression in the 1930s increased the practise as scrap metal prices dropped and it was no longer worth holding onto old hulks. However, after a number of incidents of ships not sinking on target and running aground, Commonwealth legislation was introduced around the practise.

This resulted in the formation of Commonwealth Area #3, a circular zone approximately 6km across that lies 10km south west of Barwon Heads. There’s much more information about the Ship’s Graveyard  and the history of diving its wrecks at the Red October site. The sea floor in this area lies between 40 and 60m, with a large number of wrecks in the 45m range. With a longer boat run out to these sites and the depths required, it takes a bit of good weather luck and some planning to get a successful dive in.

About the dive

Chimney on the Sir William McPherson I did this dive on a light trimix mix, using helium added to my breathing mix to reduce the narcotic effect of nitrogen at depth. Without this, I find taking decent photos past a certain depth is almost impossible, especially when trying to think about aperture/shutter speed combinations under the influence of nitrogen.

We dropped down the shot directly onto the wreck, with cloudy conditions up top meaning very little sunlight was making it through 55m of water. Even in relatively good vis, this was a dark dive. There were a few different schools of fish hanging around, with a gentle current running – very noticible when you’re pushing a camera and deco bottles through the water with every fin kick.

About the shot

This was one of the few parts of the wreck covered in the yellow zooanthids, and these really stood out in the dark conditions. I tried shots from different angles and struggled to get the strobe positioning right to reduce backscatter. Turning the strobes up to combat the dark conditions led to very spotty pictures, and eventually I widened the aperture to 6.3 and increased the ISO to 400, to allow less strobe power. On the downside, this has resulted in soft edges to the picture.

More light in this shot would be helpful in increasing the options for aperture and ISO. However, as well as the backscatter problem, increasing strobe power leads to the background going from dark blue to black as the camera is unable to pick up any natural light at all. I had also optimistically strapped an off camera strobe set up to my buddy, only to find that what I considered dark conditions still contained too much ambient light to be able to trigger the remote slave sensor.

I like the shape and colours in the shot, and it’s always nice to see schools of fish – definitely not a feature of most of my cave diving. I’m not entirely convinced that fish make it worth dealing with the technical difficulties of deep(ish) wreck photography though!

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