- When you use an
external light source instead of the camera's built-in flash you can
improve the underwater image quality by reducing back scatter (light
reflected from suspended particles between the subject and the lens.
It looks like a snow storm.). In some underwater cases, the flash built-in
to the camera is obscured by the housing, or wide angle lenses that
have been added to the camera housing, but can still be used to trigger
a slave flash.
- External lighting
can be provided either by flash or by video lights, but flash usually
gives the best results by freezing action provided that the triggering
and exposure control systems operate correctly. The video light has
a different (warm) light color than flash and the camera will have to
use internal auto color balance to correct for this or you can, on some
cameras, control the white balance with the control menu in the camera.
- Pre-flash Cameras:
Many digital cameras use a pre-flash system, whereby the cameraùs flash
fires twice. The first flash is for the camera to adjust the exposure
and set the focus distance and second to make the final exposure. This
action will pre-trigger a conventional slave strobe (cause it to fire
at full power during the pre-flash, and fail to fire during the main
flash which occurs a 200 milli-seconds later). If your digital camera
does not use pre-flash, you may be able to use conventional non-digital
slave-flash strobes. To get the best results, a TTL slave system or
varying the flash output manually will be required to make the correct
exposure. You can see the results played back on the camera's LCD and
make further adjustments to get the correct exposure.
- If you are not
sure about your equipment, or want to have the option to upgrade to
a pre-flash camera, use only pre-flash compatible strobes such as the
Ikelite digital series or the Epoque 150D Full-flash Cameras: Some cameras
fire the internal flash at full output and control exposure by adjusting
the sensitivity of the imaging device (CCD). Such cameras should be
used with a variable-output manual slave-flash such as the Epoque ES-150DS
or Sea & Sea YS25DX or YS90DX, or with a video light. Note that
the Ikelite TTL DS-125 also has a manual variable-output mode, but it
will not be possible to use the TTL function with a full-flash camera.
- Metered-flash cameras:
A more sophisticated digital camera uses a built-in light-metering sensor
to control the output of the cameraùs built-in flash. This includes
the Olympus 3040 and 4040 cameras. This may be either a TTL sensor,
or a sensor on the body of the camera. Control is achieved by switching-off
(quenching) the flash when sufficient exposure has been achieved. In
this case, the Ikelite 50D with the Remote TTL sensor (cut-off detecting)
slave flash system will provide best results by making full use of the
camera exposure control system.
- Cameras with flash
connector: Nikon Coolpix 950, 990, and 995 cameras are provided with
a sync connector. Ikelite housings for these cameras bring the sync
connector out to a bulkhead socket, and may be used, via a conventional
sync cord, with any Ikelite TTL Substrobe (i.e. DS-series strobes and
conventional Substrobes from the film-camera equipment. The Tetra and
Subal housings also have this ability for the Nikon 5000 system Flash
Trays and brackets.
- Once you know
what lighting system you will use with your camera then you need to
find the proper way to attach it to the housing. Some lights come with
an arm or bracket suitable to connect to several housings, as is the
case with most Ikelite systems. Others require a bracket (arm and tray)
to be purchased separately. Some housings (e.g., Ikelite) are supplied
with a tray, most others have a 1/4" tripod socket on the bottom
and will attach to a standard tray.
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