I am trying to create a filter adapter using 3D printing and need a bit of expertise from those who have already tried. My idea is to create a cylinder that slides onto the lens from the back. Because I know from everything I've read, that you cannot go flush over the lens hood petals without causing vignetting I was planning to then let the cylinder go outward. This is my first prototype in the software. Subscribe to see EXIF info for this image (if available) Unfortunately I don't have my own printer and have to rely on online printing services to get this done. This means prototyping via trial and error is going to be massively expensive. (about 35€ per try) I currently don't have any filters of that size and I am wondering which filter size I need to plan this for. The biggest size of filters that I could usually find on amazon was 82mm. However, I would need to attach a filter ring onto the adapter and I cannot find any 82mm rings. Just adapters from smaller sizes (although I could take a cheap filter and remove the glass). In an ideal szenario I would have a step down ring onto 82mm from something larger providing me with a bit of leeway. The big question I ask of those who have experimented with p7-14 filters. Do 77mm filters suffice? Do 82mm suffice. Or do I need something larger in terms of filters and where would I get that from. I have also considered filters that go into Cokin Style filter holders. However they seem unnecessarily bulky and inconvenient, and seem to go for quite a lot of money. Any tipps are very much appreciated. If I get this thing to work I'll also happily share the file so that you can get this printed yourselves.