http://www.adorama.com/alc/taginfo/smudge <p><span style="font-size: small;">HT stands for Hi-Trans, a proprietary multi-coating process, but do these Made In USA filters do more? And can you really clean them with a paper towel without scratching them?</span></p> http://www.adorama.com/alc/article/12912 <p><span style="font-size: small;">The best way to keep lenses and filters clean is not to get them get dirty in the firstplace. This may sound trite, but every cleaning carries with it a very small risk ofcausing problems. </span></p> http://www.adorama.com/alc/article/8110