In article
>Will an orange 85B conversion filter have the same effect on black and
>white film as a true orange filter (No. 21)? I know well enough that >the 85B has a 2/3 stop correction and the 21 has about a 2 stop >correction. Does the same apply for the No. 47 blue filter (2 1/2
>stop correction) versus an 80A conversion filter (2 stops correction)?
The filter factor gives you the answer: the conversion filter is not
sharp cut, so there will be less effect on B&W film when using it,
but it is worth a try, anyway (at least the orange one - the blues,
on the other hand, may not be too useful, unless you like the look of
very early film types...).
Hope This Helps