I compared readings from my XTi's meter and the Soligor spot meter, and the Soligor is consistently giving me readings of one stop more exposure than the XTi's meter. After comparing exposures a few times, I decided to take some pictures. First, I took a picture using the XTi's reading and then another using the Soligor's reading. I think the Soligor is actually giving the more accurate reading.
I was getting my meter readings by metering the wood of our deck, which is a bit brighter than zone 5, but if both meters were metering for zone 5, there shouldnt have been a discrepency if both meters were calibrated the same, right?
Oh, and before anyone bashes me for using a digital camera for comparison, I also used my K2 and got the same 1 stop discrepency. The reason I used digital to take the test pictures is instant feedback.