I gotten a simple UV detector (only agregates ABC) and decide to see how well each camera filter fare. Hoya HMC UV, Polarizing filter, my spectacles, plain lens scores the best. Follow by no brand gradual ND. My coffee pot is the worst.
Meter with and without filter under the sun.
Coffee maker glass pot - no protection
Coffee maker pot with 3 inch water - 25%
Clear plastic container - 25%
Hoya Skylight filter - no protection.
Hoya Pro Clear Filter - 25%
Hoya HMC UV - 100% *
Sigma UV filter -25%
Tiffen, Vitacon UV - 25%
Polarizing Filter - 90% at least
Transition spectacle lense - 100% *
Non transition seiko plastic spectacle - 100% *
85mm lens end without filter (with light beam at meter) - 100% *
China made gradual ND dark end - >75%
China made gradual ND clear end - 50%