Sigma Corporation: Information from Answers.com

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Sigma Corporation (株式会社シグマ, Kabushiki-gaisha Shiguma^?) is a Japanese company founded in 1961, manufacturing cameras, lenses, flashes and other photographic accessories. All Sigma products are produced in the company's own Aizu factory in Bandai, Fukushima, Japan. Although Sigma produces several camera models, the company is best known for producing lenses and other accessories that are compatible with the cameras produced by other companies.^[1]

Sigma produces products to work with cameras from Canon, Nikon, Pentax, Konica Minolta, Sony, Olympus and Panasonic, as well as for their own cameras.

Sigma lenses are usually less expensive than the equivalent offering from the manufacturer of the camera body in question, so are therefore often sold bundled with a camera body as a less expensive alternative to the manufacturer's body and lens kit.

Sigma's digital SLRs, the SD9, SD10 and SD14, are unusual in their use of the Foveon X3 image sensor. All use the SA lens mount. The Sigma DP1 and DP2, high-end compact P&S cameras, also use the Foveon X3 image sensor, which gives them a much larger sensor than other cameras of this type.

1 Cameras
2 Lenses
3 See also
4 References
5 External links

Cameras

Sigma has made a number of film SLR cameras, including the SA-300, SA-5,SA-7, and SA-9. They presently are making a DSLR, the Sigma SD14, the successor to the Sigma SD9 and Sigma SD10, all of which use the Foveon X3 sensor.

All Sigma SLR and DSLR cameras use the Sigma SA mount, which is mechanically similar to the Pentax K mount and electrically an adaptation of the Canon EF lens mount lens control system.

Sigma also produces a high-end compact digital camera, the Sigma DP1, using a similar 14 MP Foveon X3 image sensor to the Sigma SD14 DSLR.

Lenses

Sigma makes autofocus lenses for the Sigma SA, Canon EF, Nikon F, Minolta/Sony α, Pentax K and Four Thirds lens mounts. Each lens may not be available in all mounts, and may lack certain features (such as HSM) on certain mounts. There have been some complaints of quality control and assurance issues of lens manufacturing.^[2]^[3]

Designations

Sigma 200–500mm F2.8 EX DG

Aspherical
APO — Apochromatic lens element(s)
OS — In lens "Optical Stabilization", analogous to Nikon VR or Canon IS
HSM — "HyperSonic Motor", in-lens ultrasonic motor, analogous to Nikon SWM (AF-S) or Canon USM, etc
EX — "Excellence", professional series.
DG — Coatings optimized for Digital SLRs, still usable on 35mm or full frame
DC — Lenses for DSLRs featuring APS-C size sensors only
DF — "Dual Focus", lens features clutch to disengage focus ring when in AF mode
HF — "Helical Focusing", front element of lens does not rotate (useful for polarizing filters and petal lens hoods)
RF — "Retro-focus", this lens employs a retro-focus design to allow for unique focal length and aperture combinations.