We’ve mentioned photochromic lenses before on MAC, following the MAIB’s report on the loss of the yacht Ouzo and her crew and the possible involvement of the ro-ro ferry Pride of Bilbao. These lenses automatically darken or lighten depending on ambient light levels and had been worn by a lookout on the ferry. Now, the Australian Maritime Authority has issued a safety notice that such loenses should not be worn for lookout duties at night (See also IMO circular MSC.1/Circ1280 Night-Time Lookout – Photochromic Lenses and Dark Adaption).
Although not apparent to the wearer, even under ideal conditions such lenses have significantly reduced light transmission properties compared to ordinary lenses making it less likely that navigation lights will be seen.
So, no matter how cool they look, don’t wear them on lookout at night.