Chapter 9- Underwater Photography
Underwater Photography
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that can be added underwater, and many cameras have
a “zoom” lens that will allow focal length to be easily
changed at any time. By focal length, the area included
in a photograph can be varied, depending on the type of
picture wanted and the diving conditions. Lenses or zoom
lens settings are classified as close-up or macro, wide
angle, standard, or telephoto. In underwater photography,
wide angle lenses are usually preferred because you
can get closer to your subject for better lighting and with
less diffusion and backscatter, and still fill the frame.
The speed with which the film or camera sensor
captures the image is called its “ISO.” The higher the sensitivity
rating number, or ISO, the less light is needed to
properly expose the photo. A digital camera in automatic
mode will select an appropriate ISO within its limitations,
or it can be set manually with a few clicks of the camera
settings. If you use a film camera, you select the film of an
appropriate ISO when you load the camera. You will learn
more about the pluses and minuses of lower and higher
ISOs in your NAUI Underwater Digital Imaging course.
A strobe or flash unit has already been identified
as an important item of equipment for the underwater
photographer. Strobe units, like cameras, are amphibious
or may be enclosed in a housing. The underwater strobes
of today offer many features such as automatic exposure
control and variable power settings. As you learn more
about photography, you will become familiar with the
advantages and application of more sophisticated strobes.
There are many accessory items for underwater
photography. The accessories may be useful or essential.
Examples include trays to hold the camera and strobe
bracket, arms to hold the strobe(s), attachments for taking
close-up pictures, filters and diffusers, etc. The more you
learn about underwater photography, the better acquainted
you will become with the purpose and use of the various
accessories.
All of the components for underwater photography
are typically combined into a “system” to allow for ease
of handling. In underwater camera systems the camera,
strobe, and various accessories are connected together to
form a unit which can be handled effectively while diving
(figure 9-4).
FIGURE 9-4. Underwater photographers use racks on which to
secure the various separate pieces of the camera and
its accessories to make it easy to handle underwater.
Be very conscious that the equipment you will be
using is subject to water pressure and an otherwise harsh
environment. It requires proper, careful preparation and
care to protect it from the elements it will encounter
BASIC PRINCIPLES
The most important consideration in underwater
photography is proper exposure. This is controlled in several
ways. You have just read about sensitivities, so that is
one way of controlling the exposure. Another method to
control exposure is with the camera controls. The size of
the aperture or “f-stop” can be varied to admit more or
less light (the higher the f-stop number the smaller the
aperature), and the shutter speed (the length of time the
shutter remains open) can also be varied to affect exposures.
During your Underwater Photography Specialty
course you will learn the relationship between f-stop,
shutter speed, and ISO settings.
Another means of controlling exposure is by use of
artificial lighting. The use of an amphibious strobe can provide
light in closer proximity and in a greater amount
than the available natural light (figure 9-5). This allows
more color to be captured and for sharper images