ancillary lenses

  • Get Close, Then Closer Still!

    It’s not unknown for experienced and often professional photographers to come to Ocean Leisure Cameras, seeking out an underwater housing to enable them to take their camera underwater. We are always pleased to help._FFF6172 Nevertheless, often these people are acting under the misapprehension that in order to get good pictures whilst fully immersed in water they need to do little more to adjust the techniques with which they are familiar when working surrounded by air, than to keep their camera dry. This is not the case. Water is a very different medium to air. For one, it never has the clarity of air, neither does light pass through it without being absorbed. That doesn't mean it’s simply darker. Water absorbs light selectively. Light passing through couple of metres of water will have its spectrum distorted as the long wavelengths at the red end of the spectrum get filtered out. A few more metres and the green element is lost. Finally, only the short blue wavelengths of light penetrate very far. that is why the clearest seawater looks blue when viewed from the top. A colour-correcting filter, white-balancing in the camera or adjusting during post-production of a RAW file in the computer can help immensely when photographing in the relative shallows. The detritus in solution in the water also acts as a diffuser. Natural light underwater naturally always comes from above but often it is flat and uninteresting. Underwater, the photographer needs to add some artificial light not only to restore the natural colours but to add contrast to the photographs he takes. You might take an enormously powerful underwater flash or strobe with you but its range is still limited. Just like light from the sun, it will be filtered blue by the time it has passed little more than a couple of metres through the water t the subject and back again to the camera. So the cardinal rule of underwater photography is to get as little water between your camera and what you are photographing. Get close, then get closer still. In order to restore and image of the whole subject, it’s necessary to use a wide-angle lens - and one as wide as possible. These can be either ancillary wet lenses or prime lenses behind a dome port. Long focal-length lenses are simply of no use unless you are using a macro lens. Here’s an example of a photograph taken by natural light in the gin-clear waters off Cyprus. The Eastern Mediterranean has some of the lowest plankton levels of any seas in the world.

    Diving off Cyprus Diving off Cyprus photographed with natural light and white-balanced..
    _FFF1621 Even here in bright sunlight close to the surface skin tones are looking pallid and shadows filled in.
    Once you get a bit deeper, as in these pictures taken in Truk Lagoon in Micronesia, you’ll notice that the light from the off-board flash no longer reaches the diver and at a distance she is reduced to almost little more than a shape without detail, even though the picture was taken with the widest-angle lens available and she is little more than four metres distant.
    Diver on the wreck of an armed merchantman in Truk Lagoon. Diver on the wreck of an armed merchantman in Truk Lagoon.
    At a distance of only a few metres the diver is almost monochromatic. At a distance of only a few metres the diver is almost monochromatic.
    The nearest part of the coral encrusted deck gun is lit sharply in full colour but the mast behind is almost lost in the mist of particularly clear water. The close-up has been cropped to replicate the angle-of-view of a 60mm (standard) lens on a full-frame camera. Once you find yourself in water that’s not as clear as in the two previous examples, the difficulty in using anything with a focal length of a standard lens or longer becomes even more apparent. SafetyStop SafetyStopThis is because the water is not clear and affecting the contrast and sharpness of the image (as in the image above). The solution is to get closer, use a wide-angle lens and add contrast with an ancillary light or underwater strobe.

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