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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.
Contrast
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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