CATHEDRAL LIGHT
With photography, there are confusing exceptions
to the rules. Cathedral light refers to the focused
beams of sunlight that you can see within shipwrecks
and caverns or adjacent to overhanging marine or
plant life. Because this effect is viewed against dark
or shadowed backdrops, demarcated rays are visible
in relatively deeper water. Also, because these rays
are viewed when the sun penetrates the crevices of
the backdrop structure, they require a bright sun at
a specific angle. Mid-day might be the best time to
capture the effect in a kelp forest, but a cave opening
facing east might work best in the morning light.
Since the backdrop in most of these scenarios is
dark, your approach to exposure may be quite different
than for shooting sunrays during shallow reef dives. A
fast shutter speed will help to freeze the light beams,
but if it’s too fast your image won’t show the detail
of the surrounding structure. In this case, a bit of
experimentation will help fine-tune the balance between
sharp sunrays, detail and visible open-water colors.
Metering the light of the open water and adjusting your
settings accordingly can provide a good starting point.
Or you can simply bracket. A digital LCD screen will
reveal a good approximate starting point, and exposures
with apertures above and below that are good insurance
to ensure an optimal RAW image.
FOREGROUND FORETHOUGHT
When you incorporate strobe-lit foreground subjects,
shooting toward the sun can get very tricky. We’ve
mentioned that in extremely bright conditions it’s often
necessary to adjust camera settings to limit the amount
of light reaching your camera’s sensor. Increasing
shutter speed is one way to decrease background
exposure, but when you are shooting with a strobe
illuminating foreground subjects, your adjustments
are limited by the top synchronization speed of your
camera. Once you begin decreasing your ISO or
aperture size, assuming your strobe light to be constant,
you are also decreasing the exposure of your foreground
subject. When you alter either of these settings for
ambient light, you should simultaneously adjust your
strobe output accordingly, either by means of the
strobe’s power settings or the strobe-to-subject distance.
For ISO a good starting point is to double your
strobe power each time you halve your ISO; i.e., if you
are shooting at ISO 200 with your strobes at ¼ power,
then decreasing your ISO to 100 should prompt you
to increase your strobes to ½ power. No doubt, this
thought process relies upon a basic understanding
of the interrelationship between ISO, aperture and
strobe power, but your skill at this technique will
be accelerated using a trial-and-error approach that
incorporates careful review of images and histograms
throughout your dive.
Even the most powerful strobes produce a finite
amount of light that is puny compared to the sun. If
you cannot adequately light your foreground subject,
you might have to adjust your expectations more
rigorously than your camera settings. Selecting smaller
subjects, for instance, such as individual branches
of soft coral as opposed to coral-covered bommies,
will allow you to get closer, which will increase the
potential light intensity on your subject. Light-colored
or reflective subjects also require less strobe power
than dark-colored or absorptive subjects.
If all else fails, one creative trick remains: the
silhouette. By using an unlit subject to block the
sun, you can singlehandedly mitigate the limitations
of strobe synchronization speed — and potentially
inadequately exposed foregrounds. For silhouettes it’s
best to choose subjects with distinguishable shapes,
such as divers or large, iconic marine life. With
luck, the silhouette becomes a critical compositional
element, allowing you to take full advantage of the
sun’s rays.
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This image of a reef and diver near
Fiji was shot at 80 feet, so the sun
appears as a loosely defined ball.
