When using, bring filter in and out of the field of view. When looking, you want to see how the shadows fall in relation to the highlights. If you view continuously your eye will adapt to see shadows better and defeat it's purpose. Forget about the color of the lens. I use a peak color, does the same thing, give you a rough reference. It's not a lab device. It won't show different curves, just what the film family sees vs. what the eyeball family sees. Film differences are moot. I haven't told mine that I have used it for color and B&W. It don't know, and I'm not tellin' it. Use it as a quick reference as to light range, just as I use my card with a 4x5 cutout and a string. A pair to use together in my opinion. It won't give me all the info I need, but, it will let me know before I even set up the tripod some accommodations I may have to make.