Mirror lenses and telescopes, also called reflex or catadioptric lenses (henceforth just “mirror lenses” for brevity), are a combination of curved mirrors and lenses. They are commonly used in reflecting telescopes and super-telephoto photographic lenses. They are known for being light and compact, but they have a mixed reputation for sometimes delivering poor image quality and contrast, creating a soft, washed-out look with poor colors. This effect is often attributed to various causes (diffraction, vignette, stray light, etc) that turn out not to fully explain the problem, and when these causes are corrected, the problem remains.