Yeaaahh more FUD.....
Anyways I look at the mean. One thing to remember is that the camera has to boil all exposure measurements down to 1 number which it uses to set the f stop and shutter speed.
Each metering mode involves different math to arrive at that number (barring spot metering which should expose the spot metered at 110 in RGB scale.
Matrix metering is a separate beast all together. Center weighted is just that. Exposure of objects in the center take priority.
As to if your meter is functioning correctly, just take a moderately well illuminated monotone surface (a white or grey wall is preferred though any very light tone is fine).
Shoot the picture, and check the histogram. It should have a strong peak LEFT of dead center which will measure 90(older models)-115. As is your average in your shot.
ALWAYS remember these words from a Leica expert:
The exposure meter is calibrated to some clearly defined standards and the user needs to adjust his working method and his subject matter to these values. It does not help to suppose all kinds of assumptions that do not exist.'
Erwin Puts
BTW: please ignore RH. He seems to have some misguided notions on Pentax metering and the ANSI standards used to calibrate them......as well as a biased opinion in their regard.....
The camera looks to exposed fine if you understood what the camera was seeing.
There are some lenses that are a bit "dark" in their exposure ie old kit lens.
PLEASE look at this article:
CameraHobby - Digital Metering and Histograms