I mentioned a few posts ago about my UV filters, and how they were giving me fog issues in my pictures. One thing that they are great for is protecting your lenses from dust and dirt and scratches and what not. But you still need to keep both your lenses and your filters clean so you don’t get spots in your pictures.
Much like cleaning CDs and DVDs, lenses and filters need to be wiped from the center to the edge of the glass, NOT in a circle. You should use cleaning solution (I used some environmentally friendly) and a clean rag. I drop a little solution in the center of the lens and wipe from the middle to the edge of the lens, repeating the same steps with both side of the filter. After you clean it, use a dry corner of the rag to do the same thing. I have been told that the lens paper does more harm than good, possibly scratching the lens, and you can buy professional, legit lens cloths if you prefer. Either way, take good care of your lenses. They deserve it and, in some cases, are worth more than your camera body.
A side note, I’m going back to old posts to put galleries in them much like my last few. Feel free to peruse!