I've seen a few threads saying that this lens doesn't work well with filters. Is that just cheaper filters or any filter? Reason I'm asking is that I'm looking at buying a 100-400 which is around $1610 online and I can get it for $1749.99 from my local camera shop. The local guy won't go lower on price but will give me $20 off on a tripod and also throw in a "PROMASTER® Digital HGX Ultraviolet (UV) Filter 77mm " which appears to be a pretty good filter. Between the filter and tripod credit the prices get very close and for a little more $$ I'd prefer going with a local shop but if the filter isn't something I can really use then the online price looks like the better option.