Four Thirds system

The Four Thirds System is a standard created by Olympus and Eastman Kodak for digital single-lens reflex camera (DSLR) design and development.

[2] Unlike older single-lens reflex (SLR) systems, Four Thirds was designed from the start for digital cameras.

[3] A few months later, an internal Kodak presentation revealed that Olympus was developing a DSLR using Kodak's KAF-C5100E 5.1 megapixel 4/3" sensor, with a tentative schedule to announce the camera at the 2002 Photo Marketing Association exposition;[4] Olympus confirmed they were developing a "concept camera" with that sensor size.

[10] Nearly all of the successive Four Thirds camera models would use sensors from Panasonic, with the sole exception of the Olympus E-400 (2006), which was equipped with a CCD but sold only in Europe.

Autofocus may be accomplished via a contrast detection process using the main imager, again similar to digital compact cameras.

Some Olympus and Panasonic manufactured camera bodies also feature phase detection auto focus built into the sensor.

The common inch-based sizing system is derived from vacuum image-sensing video camera tubes, which are now obsolete.

However, the standard only specifies the sensor diagonal, thus Four Thirds cameras using the standard 3:2 aspect ratio would be possible;[19] notably newer Panasonic Micro Four Thirds models even offer shooting at multiple aspect ratios while maintaining the same image diagonal.

For instance, the Panasonic GH1 uses a multi-aspect sensor designed to maximize use of the image circle at 4:3, 3:2, and 16:9; each ratio having a diagonal of 22.5 mm.

For example, many lenses designed by Olympus for the Four Thirds System contain internal rectangular baffles or permanently mounted "petal" lens hoods that optimise their operation for the 4:3 aspect ratio.

[citation needed] In an interview John Knaur, a Senior Product Manager at Olympus, stated that "The FourThirds refers to both the size of the imager and the aspect ratio of the sensor".

[21] He also pointed out the similarities between 4:3 and the standard printing size of 8×10 as well as medium format 6×4.5 and 6×7 cameras, thus helping explain Olympus' rationale on choosing 4:3 rather than 3:2.

Olympus' E-system camera bodies are noted for their inclusion of a wide range of firmware-level features and customization, good JPEG engine, and compact size.

The models that were marketed include: The Four Thirds lens mount is specified to be a bayonet type with a flange focal distance of 38.67 mm.

There were 41 lenses made for the Four Thirds System standard, including two that were modified and re-released in approximately 2009 with improved mechanisms but otherwise identical optics.