So I have a black Olympus 17mm f/1.8 and I'm getting a matching 45mm f/1.8 next week. I have kids, so I use UV filters to protect the lenses from accidental touches. The 45mm has a smaller filter size than the 17mm, and I have a 46mm polarizer for the 17. I know that some folks use a 39 → 46mm step-up ring on the 45mm lens to share filters. I usually buy UV filters that fit the lens and only use step-up rings for polarizers and ND filters, but I've seen that others just leave a step up ring on the 45mm. Does anyone put a 46mm UV filter on the 45mm lens via a step-up ring? Is that a dumb idea? A related question is about lens hoods. I don't use them often, but I'm considering getting one for the 45mm. Would the JJC hood for the 45mm fit over a step up ring? Would the JJC hood for the 17mm attach to a filter or step-up ring on the 45mm?