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Underwater techniques

by Brian Pitkin

Reproduced from in focus 51 (Mar. 1994)

One other important difficulty in taking photographs underwater is that water is never gin clear, there are always myriads of minute animals and plants and other particles suspended in the water. The lack of clarity limits the distance we can see to about one hundred feet even in the clearest water. More often the visibility is much less than this. The suspended particles cause loss of definition, just as fog on land does.  

So how do we overcome these difficulties? Since water is the major obstacle we try to reduce the amount of it between the camera lens and our subject by getting in close, certainly no more than one third of the distance we can see and usually much closer than this. Typically we use lenses ranging from 110mm or 50mm macro to 16mm full-frame fish-eye, but never telephoto, so that our subject, whatever its size, is usually at most two or three feet from the lens. Distortion caused by using wide-angle lenses is not a major problem as there are few straight lines underwater 

To counter the loss of light and colour, you either have to stay very close to the surface and take photographs when light levels are at their greatest (usually at mid-day when the sun is at its highest) or take down an artificial light source in the form of an underwater strobe. Even if there appears to be plenty of light you will still need a strobe for close-up shots to restore colour. However, if you introduce artificial light, the suspended particles cause scattering of the light, much of it back through the camera lens, reducing definition still further and making your photographs look as though they were taken in a snow storm. The range of the strobe will probably be limited to considerably less than twenty feet if it is to put back the colour. 

In addition to getting close to your subject, an invaluable technique for underwater photography using artificial light is to ensure that as little as possible of the light from the strobe is reflected back into the lens by particles in the water. This can be achieved by holding the strobe higher and to the left of your camera and aiming it at the subject so that only the water nearest the subject, and not the water nearest the lens, is illuminated. Any particles suspended in the water nearest the subject will be lit obliquely and not reflect as much light back. The wider the angle of the lens you use, the further from the camera your strobe needs to be.

To photograph scenery underwater either stay very shallow or use a combination of natural light and artificial light. To achieve the latter, measure the available light using the camera's meter (or a specially housed land meter) and then balance the output of your strobe, by altering its output or moving it closer or further from the foreground, to provide enough light to illuminate and restore colour to the foreground. As a precaution bracket your exposures by up to one stop if you are using slide film. 

Photographing people underwater adds a further difficulty. Most swimmers, snorkelers and divers look clumsy. Either fully brief your models and rehearse your shot before entering the water or take candid shots of them when they look natural, preferably interacting with the environment rather than looking at you and your camera. Including people in a shot is easier if you use them as small distant figures that lend scale to scenic shots rather than to make them the main subject of the photograph unless they have been fully briefed. If you are photographing people close to, remember to slightly underexpose for the skin tones - even the most beautifully tanned body_can look pale and anaemic underwater. 

Photographing fish and other active animals requires different techniques. Since you need to get close, you should move slowly so as not to disturb your subject. Set up your camera and strobe ready for use before you make the approach, so that if you are using a manual system, you need only to make minor adjustments to the focus and aperture once in the desired position. Try to photograph your subject from an interesting angle, preferably framing it so that the background is not cluttered. Getting slightly below your subject and shooting upwards helps to let the subject dominate the picture. 

Focusing underwater is not much more difficult than on land if you are using a housed SLR land camera or the Nikon RS (the only amphibious SLR camera), particularly if you are using an action finder and auto focus, which works well in most situations. Your choice of face mask can, however, be critical as you need to be able to get your eye as close to the viewfinder as possible. Remember also that the those looking at your photographs will tend to look at the eye of the subject first, if this is not sharp then the photograph may not get a second glance.  

If you are using an amphibious camera without SLR, such as the popular Nikonos range, then focusing becomes more hit-and-miss. This is partly due to refraction of light at the interface between the air in your face mask and surrounding water. Objects either appear closer than they are or larger than they are in reality. Reassuringly a subject you perceive as being a set distance away will be in focus if the lens is set to that distance. However, it is no use trying to measure the distance unless your rule is graduated in underwater units. Providing your estimate of lens to subject distance is fairly precise and you set the focus accordingly, you should have sharp results. The wider the angle of the lens you are using the less precise your estimate need to be, as wide-angle lenses have a greater depth of field.  

Composing pictures with a non-SLR camera also has its problems because the viewfinder is generally only marked to frame a subject at two set distances. If the subject is either nearer or farther from the camera than these set distances, then the centre of the subject on the resulting photograph will be either lower or higher than it appears in the viewfinder. Practice will help resolve this problem, although adjustable optical viewfinders are available which can be set to the subject-to-lens distance. These are, however, still subject to the difficulties of estimating distance due to refraction referred to above. 

Because of the difficulty of focusing and composing underwater with a non-SLR camera all extension tubes and supplementary close-up lenses available for use on such cameras are supplied with framers which delimit the distance of subject to lens and the area covered. These framers are excellent, provided that you compose your picture by getting your eye level with the top of the viewfinder and looking over it at the subject. 

Like everything else, your ability to take rewarding underwater photographs will improve with practice. Remember to move slowly through the water, set your camera, get in close, compose your photograph carefully and set your strobe to light your subject so as to avoid back scatter before you press the shutter release.