What is the Micro Four Thirds System?

Panasonic LUMIX DMC-G3 16 MP Micro Four-Thirds Camera - Back

Panasonic LUMIX DMC-G3 Micro Four Thirds Camera

Micro Four Thirds Logo

The Micro Four Thirds system (MFT) is a standard created by Olympus and Panasonic for mirrorless interchangeable lens digital cameras and camcorders design and development, announced on August 5, 2008. The system provides a standard for design of compatible interchangeable lenses and compact cameras/camcorders by different manufacturers adhering to the system. Micro Four Thirds shares the image sensor size and specification with the established Four Thirds system, designed for digital single-lens reflex cameras. Unlike Four Thirds, Micro Four Thirds does not provide space for a mirror and a pentaprism, allowing smaller bodies to be designed (including a smaller lens mount, incompatible with Four Thirds lens mount). The standard supports use of Four Thirds lenses on Micro Four Thirds camera bodies using an adapter, but Micro Four Thirds lenses cannot be used on Four Thirds bodies using a purely mechanical adapter (an optical adapter is theoretically possible but has not been announced)

In late 2008, Panasonic announced a Micro Four Thirds camera and lenses:
The Lumix G1.

Olympus also developed three cameras based on the Micro Four Thirds system:
The Olympus PEN E-PL1 12.3MP Live MOS Micro Four Thirds Interchangeable Lens Digital Camera
The Olympus PEN E-P1 12.3 MP Micro Four Thirds Interchangeable Lens Digital Camera
The Olympus PEN E-P2 12.3 MP Micro Four Thirds Interchangeable Lens Digital Camera

Like its predecessor, the Micro Four Thirds system is promoted as an open standard. As of right now the major competitor to Micro 4/3 is the Sony NEX series; most prominently the Sony NEX-5 mirrorless camera.

Sensor Size and Aspect Ratio

The image sensor of Four Thirds and Micro Four Thirds is commonly referred to as a 4/3" type or 4/3 type sensor (inch-based sizing system is derived from now obsolete video camera tubes). The sensor measures 18 mm Χ 13.5 mm (22.5 mm diagonal), with an imaging area of 17.3 mm Χ 13.0 mm (21.6 mm diagonal). Its area is approximately 30–40% less than the APS-C sensors used in other manufacturers' DSLRs, yet is around 9 times larger than the 1/2.5" sensors typically used in Digital Camera Review by Gene Wrights.

The Four Thirds system used a 4:3 image aspect ratio, in common with other Digital Camera Review by Gene Wrights but unlike APS-C or full-frame DSLRs which usually adhere to the 3:2 aspect ratio of the traditional 35 mm format. Thus "The Four Thirds refers to both the size of the imager and the aspect ratio of the sensor". Note that actual size of the chip is considerably less than 4/3 of an inch, the length of the diagonal being only 22.5 mm. The 4/3 inch designation for this size of sensor dates back to the 1950s and vidicon tubes, when the external diameter of the video camera tube was measured.

The 2009 Micro Four Thirds camera Panasonic Lumix DMC-GH1 extends the aspect ratio capabilities to native 16:9 and 3:2 image formats, by incorporating a bigger sensor matrix that uses the full diagonal of the image circle in all three formats. This is called multi-aspect capability.

Lens mount

The Micro Four Thirds lens mount is specified to be a bayonet type with a flange focal distance of circa 20 mm – half as deep as the Four Thirds. The shallow camera body specified by the Micro Four Thirds standard precludes the use of mirrors, so the cameras use a live view electronic display (either on a large LCD screen or via an electronic viewfinder) or an independent optical viewfinder. The flange diameter is about 38 mm, 6 mm less than that of the Four Thirds system. Electrically, Micro Four Thirds uses an 11-contact connector between lens and camera (Four Thirds: 9 contacts). Despite this difference, Olympus claims full compatibility of existing Four Thirds lenses with Micro Four Thirds bodies, using an adapter.

The shallow but wide lens mount will also allow the use of existing manual focus lenses including Leica M and Olympus OM system lenses, via aftermarket adapters, on Micro Four Thirds bodies. It has been suggested that the contrast-detection autofocus used by compact cameras and Micro Four Thirds requires powerful focusing motors and may not operate properly on at least some of the existing Four Thirds lenses designed for phase-detection autofocus.

Advantages, disadvantages and other factors

Compared to existing compact cameras, which are equipped with non-interchangeable lenses and smaller image sensors, Micro Four Thirds are intended to offer a compact solution with interchangeable lenses and the larger sensor used by Four Thirds DSLRs. Micro Four Thirds cameras are smaller and lighter than Four Thirds and DSLRs, but larger and heavier than compacts. Apparent background blur is increased due to the lower crop factor. This can be an advantage in portrait shots for example.

The system, unlike Four Thirds, does not postulate telecentricity as a key design rule. This, combined with the much shorter flange-sensor distance enabled by the removal of the mirror, allows normal and wide-angle lenses to be made significantly smaller and cheaper because they do not have to use strongly retrofocal designs.

Advantages of Micro Four Thirds over DSLR cameras

  • Smaller and lighter cameras and lenses;
  • Shorter flange-focal distance means that practically all manual lenses can be adapted for use;
  • Shorter flange-focal distance allows for cheaper, smaller and lighter normal and wide lenses;
  • Smaller sensor size allows for cheaper, smaller and lighter telephoto lenses;
  • Absence of mirror eliminates "mirror slap" noise and vibration;
  • Electronic viewfinder can provide real-time preview of exposure, white balance and tone;
  • Brighter electronic viewfinder in low light.

Disadvantages of Micro Four Thirds compared to DSLRs

  • The sensor size is about 50% smaller than most DSLRs, leading to the common perception that image quality is inherently poorer than APS-C based cameras;
  • Contrast detect autofocus is generally slower (albeit more accurate) than the phase detect systems used in most DSLRs;
  • Due to the absence of a mirror and prism mechanism, there is no ability to use a through-the-lens optical viewfinder. The electronic viewfinder or a separate optical viewfinder must be used instead;
  • Changing lenses can expose the sensor to dust (though equally true of all 'mirrorless' interchangeable lens digital camera designs today), compared to DSLRs which have both a mirror and a closed shutter protecting the sensor (all Micro Four Thirds cameras include Olympus' award-winning  dust reduction system);
  • Larger crop factor (2x mutliplier) means slightly deeper depth of field for the same equivalent focal and aperture;
  • Olympus Europe spokeswoman Franziska Jorke cited the autofocus and burst rate of DSLRs as still being superior to Micro Four Thirds models, along with the optical viewfinders

Advantages of Micro Four Thirds over Digital Cameras

  • Greatly increased sensor size (5–9 times larger) allowing improved low light performance and greater dynamic range;
  • Interchangeable lenses;
  • Shallower depth of field possible (e.g. for portraits).

Disadvantages of Micro Four Thirds compared to Digital Cameras

  • Physical size (camera and lenses are both larger due to increased sensor size);
  • Extreme zoom lenses available on compacts (such as currently available 30Χ models) are not available on large sensor cameras due to physical size, cost, and practicality considerations;

Common misconception about Micro Four Thirds picture quality

  • 4/3 size sensors have been commonly thought to be inherently weaker in their ability to deliver picture quality than competing APS-C sensors since the sensor is up to physically 50% smaller in sensor size. Olympus has done extensive research and development in improving the imaging capability with this size of sensor. Starting with its "TruePic V" processor based cameras with refined front-of-sensor low pass filters, Olympus has proven that the 4/3 sensor is competitive against APS-C sensors with its 12MP PEN E-PL1 model being independently tested  to out-resolve 15MP APS-C based competitor cameras and even matching an 18MP APS-C SLR camera model in actual resolution and high ISO detail rendering.
  • Recent developments in sensor technology appear to promise further dynamic range and resolution improvements for 4/3 type sensors.

Micro Four Thirds system cameras

As of September 2010, Olympus, Panasonic and Cosina (Voigtlander) have a commitment to the Micro Four Thirds system.

The first Micro Four Thirds system camera was Panasonic Lumix DMC-G1, which was commenced in Japan in October 2008. In April 2009, Panasonic Lumix DMC-GH1 with HD video recording added to it.

The first Olympus model, Olympus PEN E-P1 was shipped in July 2009.

In 2009, Micro Four Thirds cameras had a 11.9 per cent share of the interchangeable lens camera market in Japan. Figures from other markets are currently not available.

Panasonic has also announced the AG-AF100 video camera for the Micro Four Thirds system, which starts shipping in December 2010.

Micro Four Thirds lenses

As of October 2010, there are eighteen Micro Four Thirds standard lenses which can be used by both Olympus and Panasonic MFT cameras:

Standard zooms


Telephoto zooms

Wideangle zooms


Macro lenses


3D lenses

Image Stabilization - Different approaches

Of the eleven Panasonic lenses, the 8 mm, 7–14 mm, 14mm and the 20 mm are not image stabilized (IS). Whilst none of the Olympus lenses have built-in IS, all Olympus Micro Four Thirds cameras have in-camera IS, and therefore all Olympus M.Zuiko Digital lenses benefit from the camera's stabilization system. The advantage with Olympus' in-body IS is that even vintage manual focus lenses can make use of the body-stabilization when used with an appropriate mount adapter. This latter fact has added to interest in Micro Four Thirds cameras by many hobbyists, especially amongst users of traditional Leica or Voigtlander rangefinder cameras.

Lens compactness and mount adaptability

    A promise of the Micro Four Thirds standard is reduced lens size and of particular interest are the Panasonic 7-14mm ultra-wideangle (equivalent to 14-28mm in the 35mm film format) and the Olympus M.Zuiko Digital ED 9-18mm ultra wide-angle lens (equivalent to an 18-36mm zoom lens in the 35mm film format). The reduced flange-focal distance of Micro Four Thirds enables such extreme wideangle lenses to be made significantly smaller and cheaper than for a traditional DSLR, because the retrofocus optical schemes can be avoided or made less extreme.

Further, both Panasonic and Olympus manufacture an adapter to enable use of any Four Thirds lenses on Micro Four Thirds cameras. While many Four Thirds lenses accept firmware updates to enable contrast autofocusing, many others are manual-focus-only. A variety of companies manufacture adapters to use lenses from nearly any legacy lens mount (such lenses, of course, support no automatic functions.)


July 27, 2010 Panasonic has announced the development of a 3-dimensional optic solution for the Micro Four Thirds system. Specially designed lens allows it to capture stereo images compatible with VIERA 3D-TV-sets and Blu-ray 3D Disc Players.

See also

  • MILC cameras
  • Lens mount
  • Lenses for SLR and DSLR cameras
  • List of lens mounts
  • Mirrorless interchangeable lens camera

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