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Whitewater Photography Tutorial #3: Getting the right exposure.

Correct exposure was covered in the previous article.

There are a few options, for setting the exposure on a camera and I will list them in order of both convenience and accuracy. This an aspect that having an expensive camera won't make much of a difference. I've noted no better metering accuracy between a Nikon D50 and D700 while shooting whitewater. That's saying a lot when you compare the $2,000 price difference! This is where technical knowledge will level the playing field.

Unfortunately the more reliable the results, the more it can turn into work. The easiest option is leaving the camera to full auto. This of course often results in over exposed shots, and sometimes the worst, over exposed shots with motion blur. The first answer to this is switching the camera to Shutter Priority mode. You chose the shutter speed and the camera adjusts the Aperture to match, and in many cameras, the ISO speed too. This still has the general over exposure problem though, but if set to a shutter speed of 1/1000 there will no motion blur.

On default all auto settings a camera will look at the whole scene in front of it and average the exposure. In Nikon nomenclature this is "matrix" metering.

If shooting on auto or shutter-priority mode, the next best thing to do is switch the metering to center-weighted. This makes the light meter take the majority of  its reading from the center of the frame, generally where the white water is. This is more accurate but certainly not fail proof. It works best on scenes that take in the whole rapid. It can be prone to bad exposures if you are shooting a close up where a dark paddler will shift the metering and make the camera overexpose.

Next is using  "Exposure Compensation". This is an external control on DSLRs and is easy to find. If you set the Exposure Compensation to -0.7 every shot will be two thirds of a stop below what the light meter reads. Vice-versa for +0.7, every shot will be two thirds of a stop brighter. Take a picture of the rapid that is about to be run, check your histogram and adjust the Exposure Compensation until the exposure is correct. Once again this is more accurate for "whole rapid" shots but not for tight shots, because the dark paddler can throw off what was a perfect exposure.

The most accurate, and most painful mode is shooting full manual. Switch your camera to full manual, choose your ISO speed, Shutter speed and Aperture size and see what the histogram shows. Experience helps a lot here, after a while can develop a good eye for ambient light and correct camera settings to match.. On a bright sunny day, I'll generally start off with a shutter speed of 1/800, Aperture F8, ISO 100. Then I'll check the histogram and adjust as necessary. If the shot is almost bright enough but not quite there, I'd shoot 1/800 F7.1 ISO 100, which would up the exposure by 1/3 of a stop. It still generally takes me 2-5 test shots to get the exposure dialed in. Practice makes perfect, but the ability to use the histogram to dial in exposure is how digital trumps film for whitewater.

 Example photo from an overcast day: 1/800 F5.6 ISO 200.

Shooting manual is a lot more work and attention demanding than just leaving the camera on auto or shutter priority, but the results speak for themselves, it's the only full-proof way to nail the exposure every time. 

Next Up: Low Light Action.

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: Lighting

Whitewater Photography Tutorial #7: Composition 

Whitewater Photography Tutorial #8: Wide Angles

Whitewater Photography Tutorial #9: Panning

Whitewater Photography Tutorial #10: Post-processing

Whitewater Photography Tutorial #11: Sequencing
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