Smaller companies such as f.e. Tamron, Samyang, Vivitar, and Opteka also offered several versions, with the three latter of these brands still actively producing a number of catadioptric lenses for use in modern system cameras.
optics | Lens (optics) | Electro-optics | Wuhan Optics Valley F.C. | The Institute of Optics | Samyang Optics | Nonlinear optics | nonlinear optics | University of Central Florida College of Optics and Photonics | Prism (optics) | Optics | Objective (optics) | Nonlinear Optics | Lens (optics)#Types of simple lenses | lens (optics) | Grassmann's law (optics) | Fourier optics | Cooke Optics | Book of Optics | Advanced Medical Optics |