Snow, Sand, and Sky

Last modified on November 27th, 2006

Clay posted an article today talking about the snow, and how his camera tended to make everything look dark. What he didn’t realize is that his camera was actually doing what it was probably supposed to do. And here’s why.

Almost all cameras have light meters that are set up to try and make every scene around 18% grey. Some guy a long time ago looked around and realized that almost every real-world scene is made up of midtones, and these midtones are usually in the ballpark of 18%. So, whenever a camera looks at a scene, it tries to figure out the amount of exposure needed to make the subject 18% grey.

What this means is that on most cameras, if you were to shoot a solid black wall, a solid white wall, and a solid grey wall, all three exposures would come out grey (since the camera figures out the exposure needed to make the subject 18% grey, and shoots using that). In real world scenes, what this means is that if you shoot a scene that is predominently dark, you’ll get an overexposed shot (which is why skies usually come out grey), and if you shoot a predominently bright scene (like the beach or snow), you’ll typically get an underexposed shot.

On most hand held cameras you can do what is called exposure compensation, where you manually bump the exposure up or down a fraction of a stop. So if I were to shoot a beach scene using my 20D, I would dial in an exposure compensation of around +1/2 EV, causing it to overexpose it slightly (which would better mimic what the eye can see).

Unfortunately for Clay I doubt his Nokia can do that. So if you go to Clay’s blog, please increase the brightness on your monitor temporarily so he feels a bit better.

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