The Samyang 500 mm MC IF f/6.3 Mirror is a manual focus fixed aperture reflex design compact telephoto lens, primarily designed for amateur & enthusiasts on a tight budget. This f/6.3 fixed aperture version features enhanced light gathering ability over the f 8 version, & is larger in size. However it is still compact & lightweight for a 500mm lens. The Samyang 500mm MC IF f/6.3 is suitable for photographing nature, astrophotography, spy / observational photography or any situation where a low priced, relatively lightweight long telephoto is desired. The construction of the Samyang 500mm MC IF f/6.3 lens combines high quality metal exterior, styled in black & white, & offers great performance for its price. The optics feature Multi-coated (MC) coatings ensuring high light transmission. The Samyang 500 mm MC IF f/6.3 Mirror is a manual focus lens, of internal focusing (IF) design. The internal focusing design helps to reduce the likelihood of getting dust & debris inside the lens, which is much more likely an issue with external focusing (or zooming) lenses which can suck in dirt during use. 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 where possible. 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. 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 series of cropped sensor. There is a optional 2x converter (available separately) increasing the actual focal length to 1000mm. (giving 1500mm on Nikon 1.5x cropped sensor, etc). As with any converter there will be a loss of quality & light transmission (of 2 or more effective EV stops), but is a very easy & cost effective way of increasing focal length. This can also be achieved by considering the Samyang 800mm MC IF f/8 Mirror lens. The Samyang Mirror lenses can be mounted to almost any digital or film SLR body by way of low cost T2 universal adapter mounts (available separately). T2 universal mounts are available to mount to most systems, including Canon, Nikon, Sony A mount / Konica Minolta, Pentax, 4/3 etc. Sony E-Mount T2 adapters are also available. 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.