Red #25 filter will make reds a very light gray. Creates dramatic contrast between blue skies, trees, clouds, and buildings. The filter nearly eliminates all Blue UV haze resulting in sharp images of distant mountains etc. 3 F Stop Filter Factor. Orange #21 filter is ideal for everyday landscape shooting. The orange filter creates contrast, but is less dramatic when shooting blue skies than Red #25. 2 F Stop Filter Factor. Yellow #8. Filters out blue/violet/UV light. Provides contrast between all colors without being too dramatic. Great for outdoors, buildings, landscapes, and people. 1/2 F Stop Filter