Aloha all, new member here. I have a question I hope someone can answer. Does anyone know, or have a suggestion about how to keep dust out of a Canon EF 100-400mm 1:4.5-5.6 L IS lens? I do a lot of shooting at baseball games, the beach, and the desert, and have noticed dust getting in the lens. Is there a way to keep this from happening? It seems to happen more when using the zoom. Mahalo in advance for any tips/suggestions. JS