2018-09-252018-09-252018http://hdl.handle.net/20.500.12091/316Dirt, dust, and oil collect on a lens with use. Dirt, dust, and oil prevent the lens from working properly. Cleaning lenses is easy. However, if a lens is cleaned improperly, you can scratch and damage it. .A badly scratched lens may need to be replaced.en-USMechanicalBTA SkillsArticle