The Samyang 500 mm MC IF f/8 Mirror is a manual focus fixed aperture reflex / catadioptric lens. Its an extremely compact telephoto lens, & offers great quality for its small size, & even smaller price. It’s a great, low cost lens suitable for photographing nature, astrophotography, spy / observational photography or any situation where a low price & very compact, unobtrusive, long telephoto is desirable. The Samyang 500mm MC IF f/8 provides a relatively bright image for its size & focal length, & is extremely handy to carry, & weighs only 320g The exterior construction of the Samyang 500mm MC IF f/8 lens is of high quality metal. The optics feature Multi-coated (MC) coatings ensuring high light transmission. The Samyang 500 mm MC IF f/8 Mirror is a manual focus lens, The fixed f/8 aperture means there is no aperture settings on the lens to worry about. Due to the very narrow depth of field with such a long focal length it is recommended to focus with live-view to achieve accurate focus. As with all long telephoto lenses a combination of sturdy camera support / tripod, good technique, fast shutter speed, & using a remote where possible is recommended to avoid camera shake to achieve the best results. For moving objects pre-focusing on a point & allowing the subject to reach that point may yield better images. Suitable for full frame & cropped sensors, on a 1.5x cropped sensor such as Nikon will yield a 750mm focal length equivalent, or 800mm on 1.6x cropped DSLRs such as Canon EOS digital SLR camera series. There is a optional 2x converter (available separately) increasing the actual focal length to 1000mm. (giving 1500mm on Nikon 1.5x cropped sensor, etc) The Samyang 500 mm MC IF f/8 Mirror lens is able to mount to most digital or film SLR bodies by way of a universal T2 mounting system. T2 universal mounts are available separately, & allow the lens to mount to most camera systems, including Canon, Nikon, Sony A mount / Konica Minolta, Pentax, 4/3, Olympus, Panasonic etc. New T2 mounts are also available for Sony E-Mount cameras. The further benefit of T2 adapters is that for users who change their camera bodies, or have different camera systems, this Samyang lens can be quickly adapted to other systems by use of another T2 adapter. Furthermore an optional eyepiece (available separately) can be attached to turn the lens into a very compact & convent viewing scope / telescope, spotting / fieldscope. The Samyang 500 mm MC IF f/8 Mirror lens is supplied with 30.5mm Skylight, ND2, & ND4 filters as well as front & rear lens caps, & a soft lens pouch. Front filter thread of 72mm