Half-and-halfs

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Since the beginning of 2010, my monthly columns have all been about how best to use just natural light underwater. When I say natural light I mean just that! No flash illumination whatsoever. This month is no exception and I want to discuss the ever-popular technique of ‘splits’, also know as ‘under-over’s, or ‘half-and-halfs.

A word about compact cameras before we start! Splits are difficult to achieve with compacts because wide-angle adaptors are much smaller than the dome ports of an SLR. As a result, shooting splits with a compact is very much hit-and-miss but it can be done with patience, persistence, flat-calm water and some luck. It’s a tricky technique to master and can take a certain amount of patience to achieve a shot, which will satisfy you.

Equipment
The best way to capture this shot is to use a
• SLR camera
• Wide-angle lens, preferably a fisheye or fisheye zoom lens
• A large dome port on your housing. This is important. A large dome port will always handle surface swell better than a small port.

Focusing
For my split shots I use either a 10.5mm fisheye lens or the Tokina 10mm-17mm zoom. Both have a considerable depth of field, which cope with most focusing issues. If the underwater and land portions are too far away from each other, ensure you prioritise sharp focus on the foreground.
One advantage of both the 10.5mm and the fisheye zoom is that they’re both compatible with and designed to perform at their optical best behind large fisheye domes, notwithstanding the make of housing.

Exposure
What may be correct for the topside view is normally too dark for the underwater view. I advocate shooting when the sun is directly overhead (there is rarely more than a one to two stop difference) or when the sun is a little way behind your back. This keeps the exposure differential at a minimum and by bracketing the combinations of aperture and shutter speed, acceptable exposure can usually be achieved. I like the sun coming from behind my back because it illuminates the topside portion without over-exposing.

Fig 1. This example is an easy way to start practicing your split shots. All you need is a mask and snorkel. Kneeling (carefully on sand) in no more than 1m of water on the house reef at Kasai village resort, Cebu, with the early morning sun behind my back, the sky, the boat and the shallow rocks were evenly illuminated. The water was glass calm, which made it easier, but to get the horizon level I had to take at least 20 shots of this particular idea. Nikon 10.5mm fisheye lens, f11 at 1/180th sec, ISO 100.
Practice this technique in your resort’s swimming pool.

Fig 2. Tokina 10mm-17mm fisheye zoom at the 10mm end, f16 at 1/250th sec, ISO 400. Taken on the house reef of Misool eco resort in Raja Ampat. This split gives the impression of surface swell, but the water was once again flat calm. I sacrificed a boat dive to take advantage of the clear shallow water, which was at an ideal tidal height for the time of day. Had I delayed this opportunity for a couple of hours the water would have been too deep to capture the shallow hard corals. Over the years I have learnt to take advantage of the conditions there and then, having been frustrated on so many occasions with failed attempts just because I just couldn’t be bothered!

Fig 3. Same lens as fig 2, f11 at 180th sec. The pier and dive centre of Lankayan resort in Sabah, Malaysia also provides excellent opportunities for splits. Over the last four days we started early morn to take advantage of the predictable flat-calm water, the rising sun, once again from behind my back and the height of the tide, which for the early part of the week was too low to provide any decent foreground subject other than an uninspiring stretch of flat sand. It took at least 25 shots to get this one! The reason was the way in which the water line cut across the hard coral formation. I particularly liked this result with the upside down soft ‘V’ shape of the water line, which echoes the shape of the dive centre roof. The vivid blue sky and white clouds was an added bonus.