There are no CSS3 filters. CSS Filters are a proprietary extension to CSS by Webkit browsers, it isn’t supported anywhere and is not in any CSS specification, neither in Level 3 nor in Level 4.
There is a separate Editor’s Draft called “Filter Effects 1.0” here: https://dvcs.w3.org/hg/FXTF/raw-file/tip/filters/index.html but that means nothing. Implementation as well as syntax may – and probably will – change, so using -moz- -o- and -ms- prefixes will likely do harm instead of being future proof.
I’d rather wait until there are at least two implementations of that stuff in browsers