Four Thirds System
From Wikipedia, the free encyclopedia
The Four Thirds System is a standard created by Olympus and Kodak for digital SLR camera design and development. (Four Thirds is a registered trademark of Olympus Optical Co., Ltd.)
The system provides a standard which, with digital cameras and lenses available from multiple manufacturers, allows for the interchange of lenses and bodies from different manufacturers. U.S. Patent 6,910,814 seems to cover the standard. Four Thirds is not an open standard, however, as it does not meet the "allowing anyone to use" criteria commonly accepted as the definition of an open standard. It also does not meet the criteria that the standard itself and any associated intellectual property be available on a Reasonable And Non-Discriminatory basis.
Unlike older SLR systems, Four Thirds has been designed from the ground up to be entirely digital. Lens design has been tailored to the requirements of digital sensors, most notably through telecentric designs. The advantages of the system include more compact telephoto lenses (a Four Thirds lens with a 300 mm focal length would cover about the same angle as a 600 mm focal length lens for the 35 mm film standard) and more even delivery of light to different parts of the sensor.
The sensor size is 18 mm × 13.5 mm, which is considerably smaller than that used in 35 mm cameras (36 mm × 24 mm). Sensor size normally relates directly to image quality, however, the manufacturers involved claim that it should be possible to exceed the quality of 35mm film using the system and that the better optics will take better advantage of digital sensors than could be done in the traditional 35 mm form factor.
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[edit] Sensor size and aspect ratio
The name of the system comes from the size of the imaging sensor. The sensor used is a "4/3 inch" type sensor. The length is based on the diameter of a particular size of Vidicon tube — the actual light sensitive area being smaller. The actual length of the sensor diagonal is 22.5mm.
It is sometimes stated that the name refers to the 4:3 aspect ratio of the sensor used in current cameras. The long side of the rectangular photographs that Four Thirds cameras produce is 4/3 (1.33 times) the size of the short side. This places it between the usual 35 mm format (with an aspect ratio of 1.5) and a square (which has an aspect ratio of 1.0). There is little doubt that the Four Thirds standard specifies the aspect ratio, in addition to the size of the imaging circle. Claim 1 of US patent 6,910,814, mentioned earlier in this article, is quite specific:
"... said camera body having an image pickup device having an imaging range with an aspect ratio of 4:3 on an imaging surface within the image circle ..."
Additionally, it is necessary to know the aspect ratio in order to design lenses. Indeed, many lenses designed by Olympus for the four thirds system contain internal rectangular baffles or permanently mounted "petal" lens hoods that restrict the lenses to operation only with the 4:3 aspect ratio.
[edit] Four Thirds system companies
As of the 2006 Photo Marketing Association Annual Convention and Trade Show, the Four Thirds consortium consists the following companies (in alphabetical order):
[edit] Four Thirds cameras
- Olympus E-1 digital camera (November 2003)
- Olympus E-300 digital camera (December 2004)
- Olympus E-500 digital camera (September 2005)
- Olympus E-330 digital camera (January 2006)
- Olympus E-400 digital camera (September 2006)
- Panasonic Lumix DMC-L1 camera (February 2006)
- Leica Digilux 3 camera (September 2006)
[edit] Four Thirds lenses
- Olympus has made 15 lenses for the Four Thirds System, with focal length ranging from 7 to 300mm, including macros
- Sigma has made or adapted 8 lenses for the Four Thirds System
- Leica has made two lenses for the Four Thirds System, a standard zoom with image stabilisation and a fast 25mm normal lens
[edit] External links
- Official Four Thirds System site
- My Four Thirds: A Photographic Community for the Four Thirds Photographer
- Unofficial 4/3rds System Site: Information about Four Thirds compatible cameras and lenses.
- Four Thirds Photo: A Large and Growing Community That Supports the Four Thirds World
- US patent 6,910,814
- PDF of the above patent (1.7 MiB)
