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Underwater Pages UW Photo Pages |
Tools & Methods
by Chris Hacking
This page is not so much to talk about my equipment as to explain how to use it, if anybody else wants to use a similar setup. While using a Canon A80 or G12 in its underwater housing is not difficult (the only real change from land use is that the viewfinder is blocked, so only the screen can be used), I will frequently refer to things on the site that you might want to know how to do. These descriptions will probably hold for most underwater digital cameras, and possibly for most slave strobes (I haven't tried any others), with only a little adaptation.
About the gear
Specially designed underwater
housings seem to be available for all of the Canon A-series and G-series digital cameras
(similar housings are also available for other makes). The joy of these housings
is that they allow complete control over all of the camera's functions even 100'
(30m) down. (Actually, my housing is rated to 40m, or about 140'.) My slave strobe is
a SeaLife ReefMaster® External Flash. Its mounting is designed for a
ReefMaster camera, but a very slight modification makes it compatible with any
tripod-type mount (which my underwater case fortunately has, as the camera's own
mount is inaccessible inside the case).
Using custom modes
The A80 has two 'custom' modes (labeled C1 and C2 on the mode
selection wheel) that remember all of their settings and allow easy access to
commonly used configurations. On my camera, these modes are set to 'default'
values for the my two most common shooting styles: using ambient light in
shallow water and using the slave strobe while diving.
These custom modes are not exactly modes in the sense of Av
(aperture priority) or AUTO; they are more like the pre-set 'portrait' or
'fast-action' modes. However, they can be changed at will
and remember their settings even when the camera's batteries and memory
card are removed. Furthermore, using a custom mode that is set to does not
prevent temporarily changing its preset options (for example, a custom mode
preset to ISO 50 could be changed to ISO 100 as easily as if in a standard
mode like P). Changing the preset options does not, by itself, reset the custom
mode; switching to another mode or turning off the camera will cause the
settings to revert to their default when the custom mode is next entered.
However, the custom modes can be overwritten, either be creating a new
configuration from a standard mode or modifying an existing custom mode, then
storing the new settings.
Shutter Priority (Sv) Mode
The simplest high-quality mode for shallow water is Sv
(shutter priority) without the flash. In this mode, adapting to changing light
conditions is as simple as a push on the easily-accessible left or right
buttons. In Sv mode, these buttons decrease or increase the shutter speed,
allowing photography in less or more light, respectively. Leaving the ISO
on Auto is easier than adjusting it in the water,
though it may result in some grainy images that could have been avoided. I
prefer to set the ISO before entering the water: 50 for a bright day in shallow
water, 100 if there is a little haze, slightly cloudy water, or if the sun is
not very high, 200 for relatively dark daytime conditions. (Generally speaking,
I won't bother going if I don't think 100 will be sufficient.) Of course, I am
quite comfortable adjusting the ISO underwater, which provides the maximum
flexibility. It is worth noting that while the fastest reasonable speed should be
used underwater, the A80 has a limited range of f-stops (2.8 - 8.0) and you may
well find that adjusting the shutter speed will be necessary for even slight
fluctuations in light. Also note that when the lens is in telephoto mode (zoomed
in) the range of apertures decreases significantly (f4.5 - f8.0 at full zoom).
For this reason, I do not usually set the f-stop (Av or aperture priority) to
let the camera select the fastest speed; if I were to zoom in and then out
again, I would need to reset the f-stop each time. Nonetheless, this may be the
better option for people who do not change the focal range often, or who prefer
to use an f-stop of 5.0 or above (which is always available).
Aperture Priority (Av) Mode and Flash Photography
Flash photographs are trickier, at least with a slave strobe.
Without a strobe, the camera's internal light sensor will probably produce fine
images. I would suggest using Av with an f-stop of 8.0 to provide the maximum
depth of field for reducing the damage of backscatter.
However, I have found that the light sensor does not handle a slave strobe well
(it may do better with an electronically attached external strobe in a fancier
camera). The pictures are nearly always too dark when using automatic settings,
so I've found I have to set the camera in manual (M) mode, and select the ISO,
aperture, and shutter speed myself. This is not actually as hard as it sounds,
and once you are set up, the only setting you will probably have to change is
the shutter speed. The aperture should be left on f8.0, and the ISO can probably
be left at 50 all the time (the range of shutter speeds is sufficient that the
other two options should not need to be changed). However, because the camera is
not automatically adjusting for changing light conditions, you will need to
judge the distance (and therefore brightness) of each shot before taking it, and
adjust the shutter speed accordingly. This will result in a LOT of underexposed
or overexposed photographs until you get the hang of determining how long the shutter
must remain open to gather enough light at a given range. Furthermore, since the
flash has a very limited range
of usability (closer will always be totally burned out, further away
will be no better than ambient light), each picture must be
composed within that range.
Macro Photography
Most cameras have an option known as 'Macro' which is
used to take very close-range pictures. Normally, a camera can not focus on a
nearby subject, making it very difficult to photograph small objects. Macro is a
special focus mode that forces the camera to focus on a close object. However,
ordinary long-distance focus is not used in macro mode; anything more than
perhaps two feet away (this distance varies by model) will be totally out of
focus and blurry. Macro mode is represented by a small flower icon. You can
create a custom (C1 or C2) macro mode if there are a collection of setting that
you use with macro and that you want to have easily at hand.
Using macro mode underwater is not actually much harder than
any other underwater photography. It requires holding the camera very still,
which can be a problem in rough conditions (see my page on
Composing shots for more information). It also
requires getting very close to your target, of course, which most fish (even
small ones) don't really appreciate. It is not necessarily a fast capture mode
(read about shutter delay here), so
rapidly moving targets can be hard to frame properly. Perhaps the most important
thing is that a slave strobe will completely burn out the image, and using a
custom white balance with even an small flash will probably result in a too-red
photograph. I recommend using a low-power strobe on Av (f8.0 or whatever your
max is) and normal color balance for most macro shots underwater.
Setup Custom Modes, White Balance, and More Settings
To set the custom modes,
configure the camera in the way you want stored (for example, select shutter
speed priority, 1/250th second, suppress flash, custom white balance, etc.),
then press the 'Menu' button, scroll to 'Save Settings', press 'Set', select
destination mode to save to, and press 'Set' again.
To set a
custom white balance, place a
white material, such as a large sheet of plastic, on the bottom (it helps to
weight it). Place yourself (more specifically, the camera) some distance from
the white material. This should be about the total distance from your light
source to your target to your camera (S to T plus T to C). For flash
photography, your light source is the flash and you should be as far from the
white material as you are from most targets. For ambient light it is more
difficult to figure out the distance; you may have to experiment a little
(especially if you often take photos while diving but set the white balance from
the surface). Once you have the distance correct, zoom in on the white material
until it fills as much of the screen as possible, then press the 'FUNC' button
and select 'White Balance' on the left and 'Custom White Balance' along the
bottom. At this point, a message should appear on your screen instructing you to
press 'SET' to set the white balance. Make sure that the white material still
fills as much of the screen as possible, and hit 'SET'. The camera will act as
though it is taking a picture, but will analyze the colors and adjust the color
balance so that whatever it sees appears white instead of storing the photo.
This adjustment is stored in the 'Custom White Balance' option even if you
switch the camera off and remove its batteries and memory card.
; There are other settings and features that are worth knowing about the A80
and underwater cameras in general. I generally use the Vivid option, which
increases color saturation to help overcome the washed-out effect caused by the
water (vivid may not be desirable with a powerful flash). I also usually use
evaluative light metering, although spot metering may occasionally be preferable
(these options are only relevant to the automatic light sensor and shouldn't
matter in Manual mode). I also turn the flash output up to its maximum setting
for flash photography in Manual mode.
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