The Four Thirds System is a standard created by Olympus and Eastman Kodak for digital single-lens reflex camera (DSLR) design and development. Four Thirds refers to both the size of the image sensor (4/3") as well as the aspect ratio (4:3). The Olympus E-1 was the first Four Thirds DSLR, announced and released in 2003. In 2008, Olympus and Panasonic began publicizing the Micro Four Thirds system, a mirrorless camera system which used the same sensor size; by eliminating the reflex mirror, the Micro Four Thirds cameras were significantly smaller than the Four Thirds cameras. The first Micro Four Thirds cameras were released in 2009 and the final Four Thirds cameras were released in 2010; by that time, approximately 15 Four Thirds camera models had been released by Olympus and Panasonic in total. The Four Thirds system was quietly discontinued in 2017, six years after the final cameras were released.
A fisheye lens is an ultra wide-angle lens that produces strong visual distortion intended to create a wide panoramic or hemispherical image. Fisheye lenses achieve extremely wide angles of view, well beyond any rectilinear lens. Instead of producing images with straight lines of perspective, fisheye lenses use a special mapping, which gives images a characteristic convex non-rectilinear appearance.
Sigma Corporation is a Japanese company, 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 high-quality lenses and other accessories that are compatible with the cameras produced by other companies.
Advanced Photo System type-C (APS-C) is an image sensor format approximately equivalent in size to the Advanced Photo System film negative in its C ("Classic") format, of 25.1×16.7 mm, an aspect ratio of 3:2 and Ø 30.15 mm field diameter. It is therefore also equivalent in size to the Super 35 motion picture film format, which has the dimensions of 24.89 mm × 18.66 mm and Ø 31.11 mm field diameter.
The Pentax K-mount, sometimes referred to as the "PK-mount", is a bayonet lens mount standard for mounting interchangeable photographic lenses to 35 mm single-lens reflex (SLR) cameras. It was created by Pentax in 1975, and has since been used by all Pentax 35 mm and digital SLRs and also the MILC Pentax K-01. A number of other manufacturers have also produced many K-mount lenses and K-mount cameras.
The Sigma SA-mount is a lens mount by the Sigma Corporation of Japan for use on their autofocus single-lens reflex and mirrorless cameras. It was introduced with the SA-300 in 1992. Originally, the SA-mount was a dual-bayonet mount with inner (SA-IB) and outer (SA-OB) bayonets, the latter being a feature intended to mount heavy telephoto lenses, but never utilized by Sigma and consequently dropped with the release of the SD14 in 2007.
The Sigma 30mm f/1.4 EX DC HSM is a wide-aperture photographic lens made by the Sigma Corporation, equipped with a Hyper Sonic Motor. The lens was produced in Canon EF mount, Four Thirds System, Nikon F-mount, Pentax K mount, the SA mount, and the Sony/Minolta AF Mount varieties, all of the same optical formula. It shipped with a removable petal-type lens hood. The lens assumes a crop factor of roughly 1.5, and therefore is not usable with on full-frame or 135 film cameras.
The Sigma 8mm f/4 EX DG is a photographic lens made by the Sigma Corporation. It is a circular fisheye lens for full-frame cameras, and has been replaced by the Sigma 8mm f/3.5 EX DG.
An ultra wide-angle lens is a lens whose focal length is shorter than that of an average wide-angle lens, providing an even wider view. The term denotes a different range of lenses, relative to the size of the sensor in the camera in question.
The Sigma 50mm f/1.4 EX DG HSM is a normal prime lens made by the Sigma Corporation.
The Sigma 150mm f/2.8 APO Macro EX DG HSM is a telephoto macro prime lenses made by Sigma Corporation.
The Sigma 4.5mm f/2.8 EX DC circular fisheye is a photographic lens manufactured by Sigma Corporation. It is a circular fisheye lens, designed to project a 180-degree field of view in all directions onto a circular image. It is the first such lens to provide the complete circular fisheye effect on crop factor digital SLR cameras, which do not have a full 36x24mm sensor. This lens is available in Canon, Nikon, Sigma, Pentax and Sony mounts.
The Sigma 10mm f/2.8 EX DC fisheye is a photographic lens manufactured by Sigma Corporation. It is a diagonal fisheye lens. Unlike most fisheye lenses, this lens is designed for digital SLR cameras that do not have a full 36x24mm sensor. This results in a much greater fisheye effect than is possible when a full-frame fisheye lens is used with a smaller sensor. The projection type of this lens is equidistant
The Sigma 50-500mm f/4-6.3 EX DG HSM is a super-telephoto zoom lens produced by Sigma Corporation. It is commonly known as the "Bigma" because of its long and heavy body. It contains four SLD glass elements to provide correction for chromatic aberration. It is aimed at advanced consumers.
The Sigma 8–16mm lens is an enthusiast-level, ultra wide-angle rectilinear zoom lens made by Sigma Corporation specifically for use with APS-C small format digital SLRs. It is the first ultrawide rectilinear zoom lens with a minimum focal length of 8 mm, designed specifically for APS-C size image sensors. The lens was introduced at the February 2010 Photo Marketing Association International Convention and Trade Show. At its release it was the widest viewing angle focal length available commercially for APS-C cameras. It is part of Sigma's DC line of lenses, meaning it was designed to have an image circle tailored to work with APS-C format cameras. The lens has a constant length regardless of optical zoom and focus with inner lens tube elements responding to these parameters. The lens has hypersonic zoom autofocus.
The Sigma 300 – 800 mm lens is a professional-level supertelephoto zoom lens made by Sigma Corporation from 2002 to 2019 for use with analog and digital SLRs. Due to its massive size and weight, the lens has been nicknamed the "Sigmonster"
The EF 11–24 mm f/4L USM lens is a professional wide-angle lens made by Canon Inc. It was announced on February 5, 2015, and at that time was the widest rectilinear lens ever made for the 35 mm format in either its film or digital versions.
The Leica L-Mount is a bayonet mount developed by Leica Camera AG for interchangeable-lens autofocus digital cameras.
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