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by David George

Reproduced from in focus 11 (Aug. 1985)

A resumé of the Basic Course talk given at the June meeting of the Society.

Artificial light

Artificial light serves two important functions. It provides light in an area where sufficient natural light is not available for the type of film you wish to use and restores colour that has been lost due to the filtering effect of water. In using artificial light, the photographer should attempt to create a feeling of naturalness.
There are two types of artificial light available to the underwater photographer. Continuous light, such as provided by a battery powered cine light. And a pulse of light, such as provided by an electronic flashgun. These two types have different qualities?

Continuous light You can see what you are illuminating. Usually balanced for tungsten, therefore a blue filter needed (or else a reddish light).
  You can use a light meter to determine correct exposure. You need a slower Shutter speed or a larger because the light is not very intense.
  Usually gives a nice wide/diffuse bright area of light.

Not suitable for light sensitive animals, and there are many.

    Quite bulky.
Electronic flash Rapid pulse of light freezes motion. You cannot see the effect.
  Quite compact units for the output given. You need to calculate exposure unless you are using a (dedicated) auto flash unit.

Direction of illumination

A feeling of naturalness may be acheived by illuminating the subject from above or to one side. Hand hold the flash or have it mounted on a long versatile am. The distance of the flash from the subject should increase as the distance from the camera to the subject increases. A flashgun attached to the camera near the lens is no good, except for extreme close-ups. The best general compromise in to have the flash above and to the left or right (usually left# as the shutter release is on the right) at 450 to the horizontal. Illuminating the subject from beneath or from behind can give a creative effect.

Record shot, which should show the diagnostic features of the subject, may be taken by illuminating the subject from the front. If the flash gives considerably more light than is available naturally, then the background will be black. Some people do not like black backgrounds, but they do help to draw the eye to the subject. Side lighting subjects increases shadow length and can be good for certain shots.

Slave flash

A slave flash is triggered by the firing of your main flashgan. It has a light sensitive receptor. A slave flash can be used some distance away from the camera, either to provide a second source (and direction) of illumination or to simulate a 'torch' held by a diver. Since most flashguns tend to be slightly positively buoyant. weight your slave or wedge it in a suitable place. ensuring that the sensor is in a direct line to the main flash gun. If you are using two flash guns of equal output at similar distances from the subject the amount of light is doubled but exposure increases by only one stop.

Natural or available light

Your first few rolls taken using natural light of colourful reef scenes can be very disappointing. This in because the eye perceives nor* than the film. You can however improve your photographs by bearing the following in mind.?

1. To get the maximum amount of sunlight you need to dive at midday and when the surface is calm.

2. In general you need to use a faster film (200ASA or more) than with artificial light.

3. You need to use a light meter, if you do not have through the lens metering.

4. You need to bracket exposure more because you have lens control on the amount of light. Watch out for clouds!

5. Different waters have different colours. Colours can be corrected using colour correction filters (CC filters). A CC30 Magenta filter in British waters will remove some of the greenness. A CC30 Red filter in tropical waters will remove some of the blueness.

6. Natural light is no good for macro photography as there is not enough depth of field even at slow Shutter speeds.

7. Try to get as close to subject as possible. Scattering of light will mean that the further you are from the subject the more broken the resulting image will be. Absorption of light causes less contrast as distance increases.


Two types of contrast give photographic impact. Colour contrast is only really applicable when using artificial light. unless very shallow, Shade contrast can give impact with natural light

1. Light subject against a dark background i.e. transparent subjects in midwater, silver fish against dark background.

2. Dark subject against a light background i.e. silhouettes of divers. More easily achieved than light against dark.

It is important that the subject has a recognisable shape i.e. sea fans, fish, people, wrecks etc. wide-angle lenses can deal with larger subjects and seascapes. To take silhouettes, get below subject and shoot upwards towards the sunlight. Try to use the foreground aa a frame when photographing distant subjects or find a suitable light window and wait for subjects to swim into it. Genuine silhouettes can be acheived by exposing the film for the maximum light reading. To expose some detail open up a couple of stops, this may however cause the outline to break up.

Combining natural and artificial light - Balanced light

Balanced light shots are the most difficult. but most effective of all underwater photographs. They are very good for scenic shots. Auto cameras do not always produce the beet results. often too balanced. Usually you want either the natural or artificial light to be dominant. In shallow water you may get double imaging of a fast moving subject with a Nikonos if you don't pan the camera because of the slow Shutter speed required for flash synchronisation. A camera with a faster Shutter speed allowing flash synchronisation is an advantage.

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