My photo classroom had a box of stuff the teachers said us students could raid, and everything the teachers didn't want (One of the teachers decided to hang onto the 1915ish Kodak camera) we could have. I ended up with a box of almost a complete set of Kodak Wratten Gelatin Filters, which 95% of the filers are unopened :). They are all 3x3cm, and the lenses I would be using them with have filter sizes from 52-72, depending on the lens, so if there is a filter holder that has an adjustable size, that would be nice :)

I'm a complete newbie when it comes to these rectangular filters, but look forward to using them, especially the ones that I can do some infared photography with (from what I'm told) :D

Easy - Cokin System P

Start with a starter kit like this (http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=387335&is=REG&addedTroughType=search) which includes a 52mm adapter ring, and buy other sizes of adapter rings as needed. The included book will explain the whole thing, but it's a pretty handy system. Also get the 3" x 3" gel filter holder here (http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=14463&is=REG&addedTroughType=search). Cokin also has the smaller System A, but it doesn't go up to 72mm filter size.

Handle the gel filters carefully. They have a way of becoming a handful outside on a windy day... :)

Cool thanks! I was looking at the Cokin one, but wasn't sure if it would work or not.

Works great, used it plenty of times. Plus you're all set if you want to use aone of their grad ND filters (although two carefully placed pieces of gaffer's tape work at least as well for this too). Don't waste your money on their lens hood and lens cap.