Sigma is one of the younger and more entrepreneurial of the Japanese camera companies, founded in 1961 as Setagaya-ku, changing its name to Sigma in 1970. It's a very small company in terms of infrastructure and permanent employees.
Sigma terminology used in their product descriptions:
- APO: lens uses multiple low dispersion elements
- ASP: Aspherical lens elements used
- CONV: Lens can use the Sigma APO teleconverters
- DOCK: Capable of being updated and tuned using Sigma's USB Dock and software
- EX: Professional grade lens; zoom maintains aperture at all focal lengths
- HSM: Hyper-Sonic Motor; internal lens autofocus motor that is quiet
- IF: Internal Focus
- OS: Optical Stabilization system; compensates for camera movement
- RF: Rear Focus
- SMC: Super Multilayer Coating
- TSC: Thermally Stable Composite
Sigma, like some of the others, has some confusing product line designations:
- DC — lenses for DX sensor cameras
- DG — lenses for FX sensor cameras
- DN — lenses for mirrorless cameras
As if that weren't enough, Sigma also now categorizes new lenses into one of three concept lines (read: marketing pablum):
- Art — designed "with a focus on sophisticated optical performance and abundant expressive power." Consists mostly of large aperture prime lenses, wide angle, and macro lenses. Examples: 30mm f/1.4, 35mm f/1.4, 18-35mm f/1.8, 24-105mm f/4, and 50mm f/1.4.
- Contemporary — "combining optical performance with compactness." Consists mostly of zoom lenses. Examples: 17-70mm f/2.8-4, 18-200mm f/3.5-6.3, 150-600mm f/5-6.3.
- Sports — "high action-capture performance." Consists mostly of telephoto lenses and exotic telephotos Examples: 120-300mm f/2.8, 150-600mm f/5-6.3.