Path: utzoo!utgpu!watserv1!watcgl!awpaeth
From: awpaeth@watcgl.waterloo.edu (Alan Wm Paeth)
Newsgroups: comp.graphics
Subject: Re: Color scanning (Wratten Filters for Separation Work)
Keywords: Kodak Wratten filters, colour separation
Message-ID: <12887@watcgl.waterloo.edu>
Date: 9 Jan 90 22:43:29 GMT
References: <720004@hpvcfs1.HP.COM> <1941@hydra.riacs.edu> <5442@udccvax1.acs.udel.EDU>
Reply-To: awpaeth@watcgl.waterloo.edu (Alan Wm Paeth)
Distribution: na
Organization: U. of Waterloo, Ontario
Lines: 23

In <5442@udccvax1.acs.udel.EDU> cygnus@vax1.acs.udel.EDU (Marc Cygnus) writes:
>In <1941@hydra.riacs.edu> hitchner@same (Lew Hitchner) writes:
>> The filters you should buy are called wratten filters...
>
>Quite correct, Lew. Perhaps the following information would be of use...
>
>Kodak Wratten gelatine filters (you can get glass, but I chose the gels)
>No. 29 (red)	#149 5621  \
>No. 61 (green)	#149 5894   +-- Kodak catalogue #s for 75mm x 75mm
>No. 47 (blue)	#149 5787  /

NOTE: most often the 25 Red and 47B Blue are employed for photographic color
separation work -- the set you choose may be different as a function of the
underlying CCD array (or film, photomultiplier tube, etc.) For what its worth,
my reference on commercial printing freely substitutes a 29 red in some cases
but cautions against use of the blue "straight 47" as an alternate to the 47B.

If someone has a copy of the Kodak Wratten filter book on hand perhaps they can
furnish numbers on the cutoff points? It would be nice to know the whole truth.

     /Alan Paeth
     Computer Graphics Laboratory
     University of Waterloo