Surface reflection reduces the amount of light transmitted through a lens, but this is not the only adverse effect. Reflection within the lens also causes such problems as image duplication, and the transmission of non-image light to the image: phenomena known as ghosts and flares, respectively. Ghosts are created when light reflected from the rear surface of a lens is reflected once again from the front surface, resulting in a faint second image slightly displaced from the primary image. Flares appear when light from the back of the lens barrel is reflected from the lens surface onto the image. Ghosts and flares caused by surface reflection reduce the quality of the image produced.