In-Camera Metering Accuracy

I almost never use the camera's meter.

I have a couple of handheld meters that I sent to Quality Light Metrics, and I use them instead.

But if you know that it is one stop off, then just compensate and spend the savings in the repair bill on film or paper or chemicals. Put a little sticker on the camera to remind yourself if it isn't your regular camera.

That's my 2 cents worth of advice.

Meters are merely a 'suggestion' because of the fact that the meter manufacturer can choose a Constant for the calibration equation which VARIES WITHIN A RANGE OF VALUES stated within the ISO standard!!! You might get three meters of the same brand and model to all agree, but trying to get three different meters of different brands and models to agree (even if targeting the identical 18% tonality target) is idealism which is not built into the ISO standard for metering. As this Wikipedia discussion points out http://en.wikipedia.org/wiki/Light_meter, the K factor can be any value between 10.6 and 13.4, a variance of 1/6 EV

Add in the variability of shutter speed in the camera and aperture diameter in the lens, and you have further reason that precision in metering is not quite equally achievable in actual exposure in camera.

" the K factor can be any value between 10.6 and 13.4

They actually vary a little more than that but still you're talking 1/6 EV and not 1 EV. Besides if you know which factor the manufacturer is using (most modern meters have spec sheet that indicate this) then you do know what it is measuring. And yes in camera meter don't have K factor published.