this started when i found a piece of leftover polarizing foil at home. to be able to use it for my gopro hero 3 camera, i designed a lens cap with a hole. with the resulting »DIY filter cap«, you can use any piece of transparent material as a filter. just cut the transparent foil to an approximate dimension and use the DIY filter cap to affix it in front of the lens on the waterproof case. i made two versions of it, one for very thin films, and a second one for thicker foils (approx. 0.5mm). while at it, i made a version with the hole closed, which makes a formidable lens cap for the waterproof case. designed using SketchUp 8. it is optimized for a replicator 2, so you might need to resize it slightly so that it fits well when printed with other printers. it's design is inspired by bokehmans »ultimate lens cap«.