Aids to thinking in black and white
One of the oldest devices for helping to see in black and white is the Kodak Wratten 90 monochrome viewing filter. It does two things. First, by darkening the view it throws the eye’s response for a few moments towards the rods rather than the cones. Second, its amber tint counters the eye’s extra sensitivity towards yellow-green.
Live Vie w
A live preview in black and white is close to ideal, although most practical if you’re using a tripod. It gives a simple desaturation, and ignores the channel-mixing possibilities that will be available during processing.