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Whitewater Photography #4: Low Light Action
Keeping our expose to the right rule in mind, how
about those deep, dark canyons and rain fed rivers. Sometimes they have
the most epic scenery but can be hard to photograph well. I'll tackle
the second most common issue in whitewater photography, motion blurred
photographs.
When there is not enough light to shoot
our ideal settings, it's time to play a game of balance with our three
previously mentioned controls, Shutter Speed, Aperture and ISO.
First we can adjust our shutter speed, because the
slower the shutter the more light we let in. The problem with this is
that rarely do you want motion blur in a kayaking shot. I consider my
slowest acceptable shutter speed to be 1/500 to 1/800 depending on the
situation. You will have to judge this based on the speed of the
paddler and water. If you are freezing motion at the top of a
waterfall, both the paddler and water will be going slow enough that
1/500 might work (although paddle blades can blur).
The paddler is nice and crisp but a blurred paddle blade and splashes make it feel soft overall.
Nikon D200. Nikkor 18-200 @ 70mm. Shutter: 1/500 Aperture: F5 ISO: 500
On the other hand, if you are trying to freeze
action at the bottom of a waterfall,, it's will be moving much faster
and harder to freeze, and thus will blur. Shutter speed is the weakest
of the three methods for adjusting exposure on dark days, because you
only gain one stop of light going from 1/1000 to 1/500.
ISO, the equivalent of film speed, will play a role on dark
days but has some serious drawbacks. Noise, the digital equivalent to
film grain (except it looks worse) is the most well known drawback.
Outside of noise, using a high ISO also drops your dynamic range and
the sensors ability to correctly capture color. But there are occasions
where there is no other option than to pump the ISO up. This is where
they amount of money you spend on a camera can make a big difference.
Whatever you do, do not, I repeat, do not, under-expose a high ISO
shot. If you are shooting at your camera's base ISO you have quite a
bit of flexibility to adjust the exposure while post-processing. (Which
will be it's own tutorial) At high ISO's any noise is greatly magnified
if you adjust the exposure, and this can ruin a great shot, making it
even worse than too slow of a shutter speed.
Example One: Shutter: 1/1000. Aperture: F4.8. ISO: 800. Post
production +2.5 exposure. Nikon D50 with Sigma 18-200 @ 40mm.
Example Two: Shutter: 1/640. Aperture: F2.8. ISO: 800 Post production +.25 exposure. Nikon D200 with Nikkor 20mm 2.8.
While the difference is pretty obvious, it's even more obvious when the images are cropped at 100%:
Although a good bit of the sharpness is due to
lens choice, these go to illustrate the dangers of underexposing a high
ISO shot, and the drawbacks to high ISO.
Aperture is by and far the most powerful of the
three choices. Opening your aperture from 8 to 2.8 is a full three
stops. This is the same as going from ISO 200 to 1600, or 1/1000 to
1/125. There are some downsides to large apertures. Large aperture zoom
lenses are expensive and heavy, because it takes a lot more glass to
let in all the light. Another downside is that on many lenses the
largest apertures are not as sharp and lose contrast. As a rule of
thumb you can't shoot low light kayaking with a cheap zooms and get
great results.
Option #1 is to lower your standards and shoot high ISO speeds with cheap light zooms.
Option #2 is to buy expensive fast zooms, but since they run around
$1,500 and weight as much as 2lbs they add up fast. Plus 2.8 isn't
always fast enough.
Option #3 is the route I have gone. Trade away the convenience of a
zoom for the light weight and (sometimes) cheap cost of a "prime" lens.
Prime lenses have generally been in production a long time and are
light and simple since they don't zoom. The $110 50mm 1.8 is a great
example. One full stop faster than the $1,700 24-70mm 2.8, 1.7lbs
lighter and $1,600 less! The downside of shooting primes is the hassle
of changing lenses on a regular basis, and more hiking to get the shot
you want. Sometimes you just can't get where you'd like to be too. They
are especially tough in a rainy environment, where you don't want to
expose the inside of your camera body while changing lenses.
Nikon D200, Nikkor 50mm 1.8 @ 1/500 F1.8 ISO 250.
The final problem with low light kayaking shots is
white balance. Ever notice how most dark weather kayaking shots look
"cold"? That's because they have too much blue in them, even the best
of cameras' Auto White Balance (AWB) is not perfect. As always we have
a few option to remedy the problem.
The first is to use a preset white balance that is built in. Shooting
on a cloudy day? Hold down the WB button and rotate the command dial
until you get to the cloud symbol. The downside to this method is that
it's not completely accurate as not every cloudy day is the same.
White Balance set to cloudy on a Nikon D50. Shot with Nikon D700 and Phoenix 100mm Macro.
The second is to leave the camera on AWB and
adjust while post-processing. This works well with high end cameras
that gets it right 90% of the time, but with a camera like the D50 I
found myself adjusting nearly every shot, way too much work.
Third is setting manual white balance with a gray
card. Judging from my love of doing things the hard way (manual
exposure and prime lenses) it seems like this would be right up my
alley, but it's not for two reasons.
A. It's simply too much work to set manually for every shot.
B. It's impossible to stand in the location of the actual
shot to get a true white balance, and the lighting on shore is often
different.
With the D50 I use the camera presets. With the D200/700 I use the AWB
and adjust in post processing. You'll have to judge based off of your
camera's AWB abilities.
Nikon D50 set to AWB. 1/500 F1.8 ISO 100. Shot with D50 and Nikkor 50mm 1.8.
Same shot after adjusting white balance (post processing tutorial to come)
To sum it up: Adjust to your slowest acceptable shutter speed &
largest aperture before raising the ISO. There is a fine line between
lens performance at maximum aperture and ISO degredation. For example
on the Nikon D200 I'll bump ISO from 100 to 200 before taking the 50mm
from 2.8 to 1.8, because the ISO boost effects quality less than the
limited depth of field and loss of contrast seen in the lens at 1.8.
Up Next: Focus!
Whitewater Photography Tutorial #1: Intro
Whitewater Photography Tutorial #2: What is the right exposure?
Whitewater Photography Tutorial #3: Getting the right exposure.
Whitewater Photography Tutorial #4: Low Light Action
Whitewater Photography Tutorial #5: Focus
Whitewater Photography Tutorial #6: Basic Lighting
Whitewater Photography Tutorial #7: Composition
Whitewater Photography Tutorial #8: Gear Picks
Whitewater Photography Tutorial #9: Post Processing
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