I am relatively new to this whole Dslr thing and i just purchased a sony a300. Well in my search for new accessories for my camera i have run into a question. How much difference is there between a cheap filter and a really expensive one? For instance i saw a circular polarizer and nuetral density filter at circuit city for only $15 each and then i have seen some online that cost a few hundred dollars. I am wondering what is the difference between these filters? I am by no means a pro photographer i just do it as a hobby on the weekends. So would it be better for me to go with the cheapies so i can have a bigger variety of filters or should i spend the extra $40-50 for the better know named filters?