how does the camera deal with the color white?

Answer 1

The camera does not deal with it very intelligently. Camera meters (digital or not) are not really that smart in knowing if it is looking at a pure black or pure white object. Your program 'P' mode and matrix metering might make a good guess, but it is usually inconsistent.

The camera's meter will try to render the white as a neutral gray (Zone V in Ansel Adam's terms). If you photograph a snowy landscape with no exposure compensation, you will get grey snow.

Likewise, the camera will also try to render black as neutral grey. If you photograph a black cat, it will probably come out more like a grey cat.

To get a nice textured white (Zone VII, which is two stops up from Zone V), meter on the white, then add 2 stops of overexposure from the meter's reading (use the camera's exposure compensation, or adjust your shutter speed or aperture)...this should get you within range of a decent white. If you are not sure, learn to use the autobracket function if your camera has one.

Likewise, if you meter on a black subject, underexpose it by 2 stops from the meter's reading to get it to "Zone III" (textured black).

Familiarize yourself with the 'Zone System' and experiment to see the effects.

Answer 2

White is not a colour, it is an absence of colour.