Unless you carry and take readings off 18% gray cards, the issue with 18% is irrelevant.
Originally Posted by floatingchildsface
Your meter has a built-in gray reference (the white dome), and your meter is calibrated to its own dome. As long as the meter is not out of whack, you should be able to use it with factory settings.
I enjoy discussing the different factors, but the bottom line of what I have learned is that the important factors are there for a reason and they are built into the calibration standards.
My simplest advice: Set the EI in your meter at the rated or actual speed of your film, and then change the EI if you find out you have to.
If you change the way you meter, like if you decide to start doing BTZS (Beyond the Zone System) metering techniques, then you might have to change your EI again.
Traditional Zone System spot metering with traditional N development often results in EI approximately half the rated speed. That's what I do and is why my EI is 2/3 stop "lower" than the actual speed of the film.