Advice on filters

I have purchased a new 16 - 45m Pentax lens and was wondering about which polarizer to buy as there seems a big difference in prices from various sources. Proffesional polarizers are muh more expensive but are they worth the extra cost? What about Murimba, may have the name wrong, but they are cheaper. Does anyone use them and if so are they a good buy? Also loking to buy a ND filter and a graduated filter can you get screw on versions of these or would I need to buy something akin to the cokin system.

If you buy an expensive one, you'll get good results. If you buy a cheap one, you'll get good results. Breaking/scratching a cheap one is a lot less painful financially, and it does happen.

For ND filters the screw-in versions work just fine and are more convenient, however, for graduated filters (of any description) the screw-in ones will always restrict you to having the transition right in the middle of the frame. The Cokin system (or similar) will allow you to place the transition at any point in the frame, hence they're generally preferable.

I use a Hoya Pro 1 D on both my Sigma 10-20 & Sigma 17-70, always found them excellent & the thinner profile helps avoid vigneting, not too expensive either

simon