Assuming you have enough film to spare, simply give it a try. Bracket. You could call it "wasting a roll" or you could call it "an investment in calibration"
Go outside on a sunny day (so the "Sunny 16" rule will be easy to work with). Point your camera in the opposite direction from the sun so you don't get any flare on the lens. Try to get a variety of objects in the frame, light and dark, so you can judge how well exposed the highlights and shadows are.
Set your shutter speed to the inverse of the film's rated ISO speed, and your aperture to f/16. Then take identical shots, opening up the aperture by a stop (or less if you prefer) until the aperture is wide open, keeping the shutter speed constant. You don't need to use up the whole roll. The shots don't need to be interesting or even very sharp.
Have the film developed by a reputable lab so the chemistry & temps are known to be controlled, unless you have a lot of experience at home developing.
Examine the film. If the shot at f/16 is underexposed but the shot at f/11 looks good, and the film was rated at ISO 100, then you know you need to expose the other rolls in that batch by a stop, or set your meter to ISO 50. If f/8 looks optimal then two stops, etc. Or choose a number in between if you prefer.
That will work well for negatives. For slide film you might wish to calibrate to half or third stops.
Once you've got the compensation dialed in, write it down on a slip of paper and put it in a freezer bag along with the rest of the rolls from that batch, and freeze it. That compensation value will be valid for that batch for several decades if the film is kept frozen.
Give a roll of frozen film about 2 hours at room temperature before opening it up, so you don't get condensation.
If the shots are important and the lighting is uncertain, always bracket.
Best of luck,
Sterling
--
Lens Grit
