ND sanity check

[ryanmills]

Just want to make sure im thinking about this right. If im using iso 400 speed film and a 3 stop ND filter, i should be metering at iso 50?

[C. D. Keth]

Yup, that's right.

3 stops means you half your ISO three times. 400-once>200-twice>100-thrice>50

[Preston]

This is true for an ND filter that affects the entire negative. If it's a Graduated ND then you would not adjust the ISO, but you'd need to see if the filter will provide the correct exposure for that portion of the negative that is affected by the additional density.

--P