Watching an eclipse
Andy Burns wrote:
Don't know if you'll find a full version of the relevant ISO standard
without paying the 58 swiss francs, maybe you have a library
subscription that gives access?
Doesn't matter where you live, anyone can join the Manchester Central
Library, they give access to the British Standards Online,
and ISO 12312-2 is included within the subscription.
Basically the film must transmit between 0.000061% and 0.0032% of
visible light and no more than 3% of infrared.