No, I saw that and am trying to roll it around in this ole noggin.
In novicespeak, does it work well now throughout the range? I guess it's the 2 stop comp you mention that is confusing me?
edit: okay I get it, the distance falloff is what you're saying…correct?
Double the distance between a flash and the meter and it should read 2 stops less for each doubling of the distance. That is the test for linearity of the response; no need for any calibrated light source, you just need an accurate way to measure distance and a repeatable flash.
So, yes it works perfectly.
Again, that was just the linearity test. The cheap-and-dirty calibration involved flashing a known to be good SB-28 Nikon flash, set to non-TTL auto, at various f-stops and reading the reflected value with Vivitar meter set to 'reflected light.' White wall, black wall, gray wall, it does not matter. Distance does not matter either. When the meter read the same f-stop as the flash was set for, it was considered 'calibrated.'
Realize that these inexpensive digital units just are accurate to a single f-stop. This Vivitar branded unit was also sold as Polaris or Shepherd FM800 and Novatron used to market one also: