Bill Cornett , Mar 23, 2005; 04:55 p.m.
Max-- We need more info on what you mean by "overexposed." Was the side of the subj. lit by the key light the only thing that was too hot? In general, what you want to do is think of the half-globe of the flashmeter like the face of the subject. A good starting orientation is to point it directly at the camera. However, if the difference between the light side and dark side of the subject (contrast ratio) is large, the meter might average the two sides and the hot side will get burnt.
Also, what kind of flash are you using? Is it an autoflash? Monobloc? What brand? What was it set at? Are you using a zoom lens that might have a variable aperture? Are you using an umbrella? How was it triggered? What brand and make of camera and lens? All these can be have major effects on your results.
Also, if you keep in mind that combining lights increases the amount of light on the subject, the f16 plus f8 equalling f22 is only about a half-stop or 2/3 stop off.
I have had to calibrate my meter to my various cameras and lenses. Sometimes it's as much as a full stop different than the settings. This is normal, in my experience, and what most pros have to do to achieve the desired perfection. What I require is consistency, and there the meter does OK. This is what you need to test for. If you consistently get readings that are a half- or full-stop off in the same direction with a particular lens, then you know how to compensate.
Happy shooting. -BC-