B+W neutral density filters at B & H Photo in New York
<http://www.bhphotovideo.com/bnh/controller/home?ci=1&sb=ps&pn=1&sq=desc&InitialSearch=yes&O=productlist.jsp&A=search&Q=*&bhs=t&shs=B%2BW+mm+1.8+neutral&image.x=7&image.y=8>
appear to be graded by by an exponent of the power of 10 that would
yield the filter factor. For example, an ND filter 0.3 (10^0.3 = 2) is
shown as reducing light by one stop or a filter factor of 2. Likewise,
filters labeled as 0.6 and 0.9 are lableled at reducing light by 2 and 3
stops respectively and having filter factors of 4 and 8.
The link I've given you above shows all B+W millimeter sized ND filters
labeled as "1.8". The specs state that they reduce light by 6 stops
which I think is the ND64 you're looking for. Inexplicably the spec
also labels the filter factor as 100 when it should be 64 for 6 stops.
It's also inexplicable to me that anyone would label their filters with
an exponent to a power of 10 that has to be computed to yield a useful
number.
Yes, filter factors do add together be they in stops or powers of 10.
But the CPL filter factor is not constant at 2 stops. It varies with
the degree of polarization.
Chuck Norcutt
Michael Wong wrote:
> Dear all,
> I wish to get a B+W ND64 filter for waterfall & river shots but there
> is no stock in Hong Kong. Is any website I may order for it? Would you
> please advise me if you know?
>
> By the way, a silly question, if I put a CPL + ND8 together. Is it
> totally -5 stops (CPL -2 & ND8 -3)?
>
>
> Thanks a bunch!
>
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