Quote Originally Posted by f/16 View Post
Hey, thanks for all the help guys. I have a 25a red, but may wait until I can get the R72. Since it will be a once in a blue moon thing, I'll just get a cheapie off of Ebay rather than a Hoya. If I meter at ISO 12 without filter then add filter, what ISO do I tell the lab personnel that it was shot at??
You should use the filter factor of the filter you're using to set your exposure meter by. If your filter requires a 2-stop exposure increase, you set your hand-held meter to ISO 50/18. You can check this by metering a scene then re-metering with the filter over the meter's sensor. If using a camera's TTL meter, set the meter to ISO 200/27; the meter will compensate automatically for the filter. I'd be more inclined to trust the hand-held meter; your mileage may vary.

Whatever filter factor you use, you have the lab develop the film normally (ISO 200/27) unless you need to adjust the contrast.

Some useful info here: http://en.wikipedia.org/wiki/Filter_factor

Cheers,
kevs