One uses and adjusts (calibrates) a handheld meter based on experience and proofing of many, many exposures and many permutations of the meter and the response of the film(s) used. For the record, I set my meter at basal calibration of +0.7 for straight shots using Velvia 50, with additional +1.5 polariser (additive compensation) with readings locked around a stored grey card read off in diffuse light (as Velvia is designed for). Obviously, an in-camera TTL/Evaluative/Partial meter has its place when speed and assurance of correct exposure is critical, but many of us prefer to put our brains to use, not allowing a camera to see things its own way. Not to say, however, that I allow my EOS 1N plenty of rope, though there are times when I do the thinking for it. Evaluative/matrix meters are Zone programmed and therefore can throw up curious mismatches to other styles of reading.