RE: FILTER FACTOR FOR #52

[Liam Lawless <lawless@bulldoghome.com>]

Bob,

When I forget the factors of the many filters I have kicking around here, I
simply put the offending piece of glass or resin in front of the window of
my light meter and take a reading... then another without a filter.  Works
pretty good!

Wikipedia has an entry for 'Wratten Number' that lists all the commonly
available Wrattens, and 52 ain't there.  Neither is it in the 'Filter
Substitution Table' in Wall & Jordan, where they have Wratten 11 and 23A as
light green (and 13 as medium green).  No factors, though.

Liam