Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
(A) No filter vs UV-blocking filter. (B) Yellow filter alone, yellow with UV-blocking filter, and yellow filter with one and two neutral density filters. (C) Blue filter vs blue filter with UV-blocking filter. (D) Green filter vs green filter with UV-blocking filter.
