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Tuesday, February 9, 2010

Exposing for Snow

Ice Tent
© 2010 Simon Hucko

Shooting in the snow can be very rewarding, but also very frustrating. I've already talked a bit about how the cold affects your camera (Cold weather? No problem!), but I didn't go into how snow can affect your exposure.

The main issue when shooting in snow is that your meter is going to get confused. (See here for more on how your meter works.) Because of how they're designed, camera meters tend to underexpose snowy scenes. They see all of the white, and try to normalize the scene to 18% gray. This is especially true on overcast days when the dynamic range of the scene is relatively small. If you look at the histogram of a shot taken on a day like this, you'll see a big peak in the middle, and your photo will be gray and muddy. An easy fix is to adjust your exposure compensation up a stop or so. On a sunny day the dynamic range will be larger, but your meter will expose differently depending on how much snow is in the frame (more snow will result in underexposure). This drives me nuts, and I usually switch over to manual exposure at this point. You can also ride your exposure compensation, but expect to do a lot of fiddling.

No matter what method you choose, learn to love your histogram. A quick glance will tell you exactly where your exposure lies, and what you need to do to get the exposure you want. Generally, you want the rightmost peak of the histogram to just touch the right edge. If you're shooting RAW, you may even want to blow out the highlights just a touch, as you'll be able to get them back in post. If you're still not using your histogram when you shoot, you're missing out on one of the best tools that digital photography has to offer, and I highly suggest you turn it on. It might seem like kind of a nerdy intimidating thing, but it's an extremely simple visual representation of your exposure, and a lot more accurate than trying to judge from your uncalibrated high contrast LCD (that will look different depending on what lighting conditions you're in). For a basic explanation of what a histogram is and how to use it, see here (luminous-landscape.com) - check out the "high key" example near the bottom to see what I meant by low dynamic range snow shots.

Finally, when you get to editing your snow photos, don't be afraid to boost brightness/exposure after the fact if you didn't quite get there in camera. You may also want to pull the mid tones and shadows up if you're shooting on a sunny day and exposed to hold some texture in the snow. If your photos are a little flat (overcast day), add some contrast back in to give them some punch. Consider some black and white conversions (snow looks great in black and white).

Hope this was helpful. As always, any comments or questions are welcome :)

~S

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