Originally Posted by CPorter
I think they only said 2 stops as a suggestion, since you can't practically set 1 2/3 stop.
But you can carefully note meter reading to nearest 1/3 stop, add 1 2/3 stop filter factor. Then sometimes the correct exposure (including filter factor) will fall exactly. Or you can include filter factor in the EI that you set on a handheld meter.
When I go out, I often pick the filter in advance and use it the whole day. I set the EI on my handheld meter to include the filter factor. When I go inside, then I take the filter off and set EI on the meter to rated speed.