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Whitewater Photography #3: Getting the right exposure.

As discussed in the previous article, we have a good idea of what we want our exposure to be. Now how to get it.

There are a few options, and I will list them in order of both convenience and accuracy. This is somewhere that having an expensive camera won't make a difference. I've noted no better metering accuracy between my Nikon D50 and D700 while shooting whitewater. That's saying a lot when you compare the prices! This is where your choices and skills 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 does it's best to adjust the Aperture to match, and in many cameras, the ISO speed too. This still has a general over exposure problem though.

The next best thing to do is switch your metering to center-weighted. This makes the light meter focus it's reading on 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 is prone to bad exposures if you are shooting a close up where the dark paddler tends to make the camera compensate and overexpose.

The next work around is to use "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 2/3 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 seemed like a perfect exposure.

The most accurate, and most painful mode is shooting full manual. This is where it can start to turn it into work. It can be tough to focus on if you are on a river that's already challenging, because there is that much more to think about. 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, but after a while you'll have a good idea of the relationship of light to your exposure settings. On a bright sunny day for example, 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, and using 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. Nikon D200 with Nikon 75-150 "E" @ 150mm.