I have used a Peak viewing filter for years. It is about a Wratten 90 color. It works for me and I like it fine. I'm thinking about getting another one for the other camera bag and I got to thinking about why are viewing filters amber colored. Film 'sees' mostly in the blue and blue-green and our eye sees mostly in the middle green. It would make sense to use a blue filter as a viewing filter. Then you eye would see what the film sees. So why the #90? Anyone know? I have looked around at viewing filters and see the Peak filter is still available and a Tiffen (and ZVI, but no thanks) and from the movie business there is Harrison & Harrison. H&H make a whole lineup of colors for viewing filters. Any input would be appreciated.