How and when should I clean the lens?

• Clean the lens whenever you notice dirt or dust on the surface. To remove dirt or smears on the lens, use a commercially available cloth for cleaning glasses.
  
  Caution: Do not spray liquid or glass cleaner directly on the lens. Do not rub the lens with harsh materials or subject the lens to shocks, or you may damage it. Do not use wax, alcohol, benzene, paint thinner, or other chemical detergents. These can damage the case.