Film as a different ISO for different light sources. Set your meter at the rated ISO for for the film you are using. Expose 1 fame as indicated by the meter. Now using manual aperture control, shoot what is called an "exposure series or bracketing". I suggest making a test in 1 f-stop increments. 4 then 3 then 2 f-stops under followed by 1 then 2 then 3 then 4 f-stops over. Chose the best frame and then reshoot in 1/3 f-stop increments. Make notes so you can identify the exposure setting for the frames. This way, you are computing the ISO setting for your specific set-up. This will be the ISO setting to use with your hand-held meter and that light source.

Film have a different ISO for different light sources. Set your meter at the rated ISO for for the film you are using. Expose 1 fame as indicated by the meter. Now using manual aperture control, shoot what is called an "exposure series or bracketing". I suggest making a test in 1 f-stop increments. 4 then 3 then 2 f-stops under followed by 1 then 2 then 3 then 4 f-stops over. Chose the best frame and then reshoot in 1/3 f-stop increments. Make notes so you can identify the exposure setting for the frames. This way, you are computing the ISO setting for your specific set-up. This will be the ISO setting to use with your hand-held meter and that light source.