Micro Four Thirds system

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The Micro Four Thirds system is a standard created by Olympus and Panasonic for compact digital camera design and development, announced August 5, 2008.^[1] The system provides a standard for design of compatible interchangeable lenses and compact cameras 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 Third 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.

In late 2008, Panasonic announced a Micro Four Thirds camera and lenses, the Lumix G1^[2]. Olympus also announced the development of a camera based on the Micro Four Thirds systems known as the Olympus PEN E-P1 Camera on June 16, 2009. Unlike its predecessor, the Micro Four Thirds system is not promoted as an open standard.^[3]

[edit] Sensor size and aspect ratio

Drawing showing the relative sizes of sensors used in most current digital cameras, relative to a 35mm film frame.

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 × 13.5 mm (22.5 mm diagonal), with an imaging area of 17.3 mm × 13.0 mm (21.6 mm diagonal).^[4] Its area is 30–40% less than the approximately APS-C sensors used in other manufacturers' DSLRs, yet is around 9 times larger than the 1/2.5" sensors typically used in compact digital cameras.

The Four Thirds system used a 4:3 image aspect ratio, in common with other compact digital cameras 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".^[5] 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 multiaspect capability.

[edit] 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 will 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 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^[6], 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.^[7]

[edit] Advantages, disadvantages and other factors

Concept model of Micro Four Thirds camera by Olympus

For comparison of the original Four Thirds with competing DSLR system see Four Thirds system#Advantages, disadvantages and other factors

Compared to existing compact cameras, which are equipped with non-interchangeable lenses and smaller image sensors, Micro Four Thirds is 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. The depth of field is less than all compacts, but more than in full frame cameras; it is the same as in Four Thirds DSLRs. Depending on the kind of pictures, this can be an advantage or a disadvantage (in portraits one wants shallow depth of field, in panoramas one wants large depth of field).

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

[edit] Advantages of Micro Four Thirds over Four Thirds and DSLR cameras

• Smaller and lighter cameras and lenses
• Contrast detect autofocus can be more accurate than the phase detect systems usually employed in entry-level DSLRs
• Shorter flange-focal distance means that practically all manual lenses can be adapted for use
• Brighter electronic viewfinder in low light
• Electronic viewfinder can provide real-time preview of exposure, white balance and tone
• Absence of mirror eliminates "mirror slap" noise and vibration
• Smaller sensor size allows for cheaper, smaller and lighter telephoto lenses

[edit] Disadvantages of Micro Four Thirds compared to DSLRs

• Fewer dedicated autofocus lenses available (so far)
• 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, compared to DSLRs which have both a mirror and a closed shutter protecting the sensor
• Contrast detect autofocus is generally slower than the phase detect systems used in most DSLRs
• The depth of field is wider due to the smaller sensor size.
• The high ISO performance is poorer because of the smaller sensor size.

[edit] Advantages of Micro Four Thirds over compact 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)

[edit] Disadvantages of Micro Four Thirds compared to compact 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 25× models) are not available on large sensor cameras due to physical size, cost, and practicality considerations

[edit] Micro Four Thirds system cameras

As of August 2009, only Olympus and Panasonic 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.^[8] In April 2009, Panasonic Lumix DMC-GH1 with HD video recording added to it.^[9]

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

• Panasonic Lumix DMC-G1 (October 2008)
• Panasonic Lumix DMC-GH1 (April 2009)
• Olympus PEN E-P1 (July 2009)
• Panasonic Lumix DMC-GF1 (September 2009)
• Olympus PEN E-P2 (November 2009)

[edit] Micro Four Thirds lenses

As of October 2009, there are eight Micro Four Thirds lenses:

Standard zooms

• Panasonic Lumix 14–45mm f/3.5–5.6 (G1/GF1 kit)
• Olympus mZD 14–42mm f/3.5–5.6 (E-P1 kit)

Superzooms

• Panasonic Lumix 14–140mm HD f/4–5.8 (GH1 kit)

Telephoto zooms

• Panasonic Lumix 45–200mm f/4–5.6 (G1 kit)

Wideangle zooms

• Panasonic Lumix 7–14mm f/4

Primes

• Olympus mZD 17mm f/2.8 (E-P1 kit)
• Panasonic Lumix 20mm f/1.7 (GF1 kit)

Macro lenses

• Panasonic Lumix 45mm f/2.8

Of the six Panasonic lenses, the 7–14 mm and the 20 mm are not image stabilized. Neither of the Olympus lenses are image stabilized. Of particular interest is the 7–14 wide-angle lens – 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^[6] (such lenses, of course, support no automatic functions.)

A Panasonic Leica 45mm f/2.8 macro lens was announced on September 2, 2009.

[edit] See also

• Lenses for SLR and DSLR cameras
• Lens mount
• List of lens mounts

[edit] Notes

[edit] References

• The Micro Four Thirds Standard official pages.

[edit] External links

• Media related to Micro Four Thirds system cameras at Wikimedia Commons