Back here I started talking about matrix metering, but to keep your heads from exploding in boredom broke it into a couple posts. This time, though, we get to talk about the bells and whistles of modern matrix metering, instead of the humdrum of how it works.

Scene recognition libraries. This idea also dates back far longer than I can pin down with accuracy, but the idea is the camera compares your matrix to a library of saved matrixes to see if it can better understand what you’re shooting.

For example, if you’re trying to take a picture of your Aunt Bessie (and really, shouldn’t everyone have an Aunt Bessie?) out in some snow–nice, bright, white snow–you might get a metering that looks like this:

Under straight matrix metering, this exposure might not be too bad, the bright lights and darks already balance out close to a middle grey as far as its concerned. But, we know that dark blob is really your Aunt Bessie, and she will be quite unhappy if your picture of her relegates her to the shadows.

Metering libraries would take this and run it against some scenes they have, and it’d probably run up against a similar one that tells the camera to overexpose if it sees this. Why? The camera essentially “realizes” the scene is backlit and exposes for the dark area and not the scene as a whole.

Now, the champs of advanced metering tricks right now are the newest wave of Nikon digital SLR cameras with their 3D Matrix. It’s not just reading light, but they’ve combined it with their white balance system so it can measure colors, too. They also combined all this with auto-focus, but that’s a different story. But, thanks to the advanced metering in cameras like their pro D3, the camera can tell something is a face (two really white ovals–the eyes–in the middle of an oval of another color) and not, say, merely just a chair, which could in our last example be the difference between a a nice portrait and a stunning sihlouette (whereas just regular old scene recognition would probably see both your Aunt and the chair the same way, a dark blob in the corner, and expose them both the same).

Now, I’m not saying trusting your matrix metering is the only way or even the best way to shoot, there are a few other ways I’ll talk about, but if you like running your camera on Auto more often than not, I’d say the matrix metering method is one of the digital camera comparisons you’ll probably be wanting to look at.