I have a pair of Ray-Bans with the B-15 brown colored mirrored lenses
which are great for enhancing contrast and eliminating scattered blue
light of which there is plenty at altitude. The brown lens barely
distorts color, and really helps in finding the wispies or darkest part
of the cloud. Optics are excellent with no distortion. I bought a new
pair on Ebay for $30.00. They can't be beat IMO.