Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!zephyr.ens.tek.com!tekig5!briand
From: briand@tekig5.PEN.TEK.COM (Brian Diehm)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Chroma32 color from B&W scanners problem
Message-ID: <5306@tekig5.PEN.TEK.COM>
Date: 5 Jan 90 00:01:35 GMT
References: <19640005@hpvcfs1.HP.COM>
Reply-To: briand@tekig5.PEN.TEK.COM (Brian Diehm)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 30

>The color scans don't have good color and I think I know why:  The color
>filters suck!  The red filter doesn't block all of the blue or green.  The
>green filter doesn't block all of the red or blue light etc.
>
>I played around with some red plastic sheets that I found around the office
>and came up with better colors in my scans, but still not good though.
>
>Also does anyone know where I could get decent quality colored plastic sheets
>to test as filters?  I especially need a good red filter, but I suspect that
>all of the filters can be greatly improved.

I would consider Kodak gel filters, if they are large enough. They make the
filters used in industry for color separations, and have separation primaires
in their product line. A generic "photographic red" filter (#25) will exhibit
the properties you seek - making everything you view through them appear in
the range from pure red to pure black, with no other color evident.

Generally, gel filters are available in 3-inch and 4-inch squares. These are
pretty fragile (fingerprints and moisture will RUIN them, not just damage them)
and they tend to go for about $20 each - they're not cheap.

There also exists a Kodak filter databook that gives the spectral response of
each of their filters. If you need specific references, I will look them up for
you.

-- 
-Brian Diehm
Tektronix, Inc.                (503) 627-3437         briand@tekig5.PEN.TEK.COM
P.O. Box 500, M/S 39-383
Beaverton, OR   97077                        (SDA - Standard Disclaimers Apply)