I've often seen the advice that beginners should "for one year use one camera, one lens, and one film". While not exactly a beginner I intend to try this anyway in the hope to become a better photographer. I will use my Pentax LX, my 43/1.9 limited and lots of Delta 3200. I often shoot in low light situations. I have a small case attached to the camera strap with room for three filters. Which three filters would you recommend that I should always bring with me, and why? Many thanks in advance!