Filters should be multicoated. Super-multicoated is better. Super-duper-multi - oh never mind.
The coatings actually prevent light from being reflected which means it passes through the glass instead which is a good thing.
There are thosse that would argue that a UV filter is not needed and is not a good thing... I've used them for years and just recently took them off (for the wedding).
You pretty much get what you pay for with filters and lenses. I would not put a $200 filter on a $200 lens though. I do put $150 filters on my $1500 lenses when I use them. The argument is that a filter, no matter how good, can do nothing but limit what the lens sees. Why buy a $1500 lens and limit what it can see right?
The argument I would follow here is the Newfie Drool argument.
You won't notice aa difference when you're starting out and a UV filter can save you some grief when drool (or sand or whatever) hits it.
So bottom line, buy the best filter you feel you can afford. It's one of those things you'll forget about once its on, but if you need to clean it you'll be glad it's the fillter and not the lens.
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