View Single Post
  #8  
Old 25th February 2014, 10:42 PM
JOReynolds JOReynolds is offline
Friend
 
Join Date: Nov 2012
Location: St Albans UK/Agde France
Posts: 1,074
Default

Relevant quote from Wikipedia : 'The number denotes the color of the filter, but is arbitrary and does not encode any information (the 80A–80D are blue, the next filters in numerical order, 81A–81EF, are orange); letters increase with increasing strength'. The Wratten series numbers begin with 8* where * means any number.
Reply With Quote