Now for the next question....When I use my thin Cir-Polarizer, which I bought because of the vignetting, it isn't thick enough to use a snap-on cap. The filter came with a rubber cap, but it falls off a lot. Is there any type of thing -- elastic, clip....that will hold the cap on? I know this seems trivial, but I don't want the filter scratched, and it's getting old worrying about and checking to see if the cap is on or off. Thanks.