I don't think it takes into account format or film.

f/1 would be full light, if I recall. That's what you'd get if you exposed the film with no lense in place. f/1.8 through f/22 are just different fractions of that light (whatever the amount you got from f/1 was), each one half the light amount of the previous.

I think the distance to the film plane and the angle of the light is usually taken into account by the manufacturer, so that on a given mount, on a given camera, the focal plane is generally the same.

On your larger formats there you might get into strange territory, but on the 35mm bodies I'm familiar with all of this is taken into consideration and light metering simply "works"...