Every modern camera has an in-camera meter, and the most common of them is the Matrix or Multi-zone meter (also called evaluative or segment meter, among other names). Surprisingly, due to complicated algorithms that work effortlessly in real time, these meters give you the best exposure ninety nine times out of a hundred. And that’s good –
If you’re a snap-shooter or tourist who just wants to use a camera to record whatever you see. The problem comes when you want to interpret a scene, to your artistic sensibilities. In that case, the biggest mistake you can make is to rely on matrix metering to make your decisions for you.
Look at it this way – if two photographers with identical cameras shoot the same scene and composition standing side by side, and both of them use matrix metering, the emotional quality of the photograph will be the same. In fact, in most situations, both photographs might almost be indistinguishable. For a lot of people this might seem okay, but for the artist, it is not.
Why not? An artist’s aim is to represent his/her art in a way that is unique to their vision of it. That’s what makes it special. If you cannot put your personal stamp on a photograph, then you are not an artist. If you look through the viewfinder or at an LCD screen, and don’t interpret the scene in front of you according to your own feelings, rationalizations, experiences or perspective, then you are not an artist. When the artist and his subjects are no more, his photographs must still communicate his intentions. I consider this as photography’s highest calling.
Photographers use and manipulate light, composition, perspective, distance, lens, depth of field, bokeh, color, tones, textures, and so on, to create their photographs. But they also use one more thing: Metering. How does an artist meter? By using the Zone System.
The Zone System was formulated by Ansel Adams and Fred Archer in 1939–1940. The technique is based on the late 19th century sensitometry studies of Hurter and Driffield. The Zone System is a systematic method of precisely defining the relationship between the way photographers visualize the subject and the final results. The key word here is visualization. The meter most used in the Zone System is the Spot Meter (which is also found in DSLRs).
To learn about the Zone System, the best place to start would be Ansel Adams himself, in his great series: The Camera, The Negative and The Print (1995). Then you can read the Wikipedia article here. A great simplified version, written by Norman Koren, can be found at Luminous Landscape here.
The Zone System offers tremendous value for artists using digital technology, and a thorough mastering of this technique improves visualization to the point where your photographs start becoming works of art.