AD 2017 Q4

IMAGING
PHOTO TECHNIQUES
LIGHT IN THE DARK: SHOOTING CENOTES
Text and photos by Alex Mustard
We kit up on a small wooden bench
beside a pickup truck, enclosed
by an impenetrable green wall of
jungle. There is no view of water
— our destination is a wooden
staircase leading down into a crack in the earth. This
is a surreal setting for a dive, and it leads to an entirely
fresh experience. If you want to expand your diving
and photographic horizons, then a trip to Mexico’s
cenotes should be at the top of your list.
The wooden steps lead down into a pool of smooth,
dark water. I slip in and dip my head into El Pit
cenote. Suddenly I feel much smaller. This tiny plunge
pool is the opening to a huge world underwater and
underground. Looking down I can see for about 100
feet, but I can’t see the bottom. In front of me the
cavern extends away into the darkness. My anticipation
and heart rate increase.
DARK DEMANDS
Crystal-clear water usually makes photography easy, but
don’t underestimate the challenges of the dark. Cenotes
— deep, natural, water-filled limestone wells or sinkholes
— are much darker than you might expect, which can
make it difficult to focus and determine exposure.
For focusing in the cenotes, I use back-button, or
thumb, focus. This mode, which most cameras offer,
allows you to decouple the autofocus from the shutter
release and assign it to a button you press with your
right thumb. This means you can focus carefully when
there is light at the start of the dive and then leave it
locked so the focus does not struggle in darker places.
A dedicated focus light is often a hindrance in this type
of photography because its beam, which will be much
brighter than the dark conditions in the caverns, will
show up in your pictures. This problem is exacerbated
by the slow shutter speeds often used.
The darkness also presents a challenge for
exposures. It necessitates using settings that are way
outside of our normal comfort zone. For example,
even the photo of bright sunbeams was at first
underexposed and needed a higher ISO of 1600, an
aperture opened to f/8 and a shutter speed of 1/25 th of
a second to achieve the look I wanted.
There are no magic numbers I can tell you to dial in.
First, cenote light levels are variable. Second, how each
of us adjusts the aperture, shutter speed and ISO from
our open-water settings will depend on our cameras.
We can push newer cameras, for example, to higher
ISO values than we could with older models and still
perform admirably. Full-frame cameras can use higher
ISOs without objectionable noise, but we may need
to use a smaller aperture to achieve acceptable corner
sharpness. Image-stabilized lenses can be pushed to
slower shutter speeds than can nonstabilized lenses.
It is best to think about your camera’s settings and
capabilities before you dive rather than trying to make
a call about what to sacrifice while underwater. As a
rule it is sensible to compromise a little on all three
settings (aperture, shutter speed and ISO) rather than a
lot on any one. Finally, breathe in slowly while shooting
long exposures, as breathing out will create bubbles
that might vibrate the camera.
The other challenge with exposure is getting it right
for the dive rather than relying on adjustments in
postproduction. This is especially important when you
shoot at high ISO values, because typical adjustments to
exposure in Adobe Camera RAW or Lightroom generate
a lot of noise. Furthermore, your LCD will shine brightly
in the dark of a cavern, making it easy to think an
underexposed image is properly exposed. If in doubt,
check the histogram or have an above-water image as
the first shot on your memory card for comparison.
SUNBEAMS
Few subjects are as beautiful or as emotive as beams of
sunlight spiking down into the water. The cenotes’ calm
water tightly focuses the rays, and against the darkness
of the caverns they elicit comparisons to laser beams.
The key to capturing them is to position yourself
in the dark, looking back at the beams. Ideally you
want a viewpoint that hides the surface, so the beams
are the brightest subject in the frame. The more you
can overexpose the scene, the brighter the beams will
be. If you haven’t hidden the bright surface in your
composition, it will overpower the rest of the frame,
and the shot won’t be as stark. You may also end up
with clipped highlights that can’t be recovered.
Adding strobe light usually ruins the ambience in
these photos, so unless there is something spectacular
in the foreground, turn off your strobes. Fisheye lenses
are usually the default choice in caverns because they
102 | FALL 2017