Canon 300/4 L FD - vom Vorbesitzer halb kaputt repariert - restauriert

[Ando]

Gibt es irgendwo eine Übersicht der jemals verfügbaren Einsteckfilter?

Drop-In Filters

There is a slot on the lens that accepts 34mm drop-in filters. I just have the 1x Regular filter that was supplied with new lenses.
Apparently, the following filters are also available: UV (Ultra Violet), R1 (Red filter to provide stronger contrast with B/W photos), Y3 (Yellow filter improves the look of blue skies in B/W photos), ND (Neutral density filter for when you want to use long exposures or large apertures in very bright conditions).
If you want to acquire one (or more) of these additional filters I would imagine your best bet is eBay although they will be quite rare, especially if in good condition.

http://phil.uk.net/photography/canon-fd-300mm-f4.html