The Four Thirds System is a standard created by
Olympus and
Eastman Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
for
digital single-lens reflex camera
A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that combines the optics and the mechanisms of a single-lens reflex camera with a digital imaging sensor.
The reflex design scheme is the primary difference between ...
(DSLR) and mirrorless camera design and development.
The system provides a
standard Standard may refer to:
Symbols
* Colours, standards and guidons, kinds of military signs
* Standard (emblem), a type of a large symbol or emblem used for identification
Norms, conventions or requirements
* Standard (metrology), an object th ...
that, with
digital camera
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
s and
lenses
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...
available from multiple manufacturers, allows for the interchange of lenses and bodies from different
manufacturers. seems to cover the standard. Proponents describe it as an
open standard
An open standard is a standard that is openly accessible and usable by anyone. It is also a prerequisite to use open license, non-discrimination and extensibility. Typically, anybody can participate in the development. There is no single definition ...
, but companies may use it only under a
non-disclosure agreement
A non-disclosure agreement (NDA) is a legal contract or part of a contract between at least two parties that outlines confidential material, knowledge, or information that the parties wish to share with one another for certain purposes, but wish ...
.
Unlike older single-lens reflex (SLR) systems, Four Thirds was designed from the start to be entirely digital. Many lenses are extensively computerised, to the point that Olympus offers
firmware
In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...
updates for many of them. Lens design has been tailored to the requirements of digital sensors, most notably through
telecentric designs. The size of the sensor is significantly smaller than for most DSLRs and this implies that lenses, especially telephoto lenses, can be smaller. For example, a Four Thirds lens with a 300 mm
focal length would cover about the same angle of view as a 600 mm focal length lens for the
35 mm film 35 mm may refer to:
* 135 film, a type of still photography format commonly referred to as 35 mm film
* 35 mm movie film
35 mm film is a film gauge used in filmmaking, and the film standard. In motion pictures that record on f ...
standard, and is correspondingly more compact. Thus, the Four Thirds System has
crop factor
In digital photography, the crop factor, format factor, or focal length multiplier of an image sensor format is the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital ca ...
(focal length multiplier) of about 2, and while this enables longer focal length for greater magnification, it does not necessarily aid the manufacture of wide angle lenses.
The
image sensor format
In digital photography, the image sensor format is the shape and size of the image sensor.
The image sensor format of a digital camera determines the angle of view of a particular lens when used with a particular sensor. Because the image se ...
, between those of larger SLRs and smaller
point-and-shoot
A point-and-shoot camera, also known as a compact camera and sometimes abbreviated to P&S, is a still camera designed primarily for simple operation. Most use focus free lenses or autofocus for focusing, automatic systems for setting the exposu ...
compact digital cameras, yields intermediate levels of cost, performance, and convenience.
Sensor size and aspect ratio
![Sensor sizes overlaid inside - updated](https://upload.wikimedia.org/wikipedia/commons/9/9a/Sensor_sizes_overlaid_inside_-_updated.svg)
The name of the system stems from the size of the image sensor used in the cameras, which is commonly referred to as a ''4/3" type'' or ''4/3 type'' sensor. The common inch-based sizing system is derived from vacuum image-sensing
video camera tube
Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
s, which are now obsolete. The imaging area of a Four Thirds sensor is equal to that of a video camera tube of 4/3 inch diameter.
The usual
size of the sensor is 18 mm × 13.5 mm (22.5 mm diagonal), with an imaging area of 17.3 mm × 13.0 mm (21.63 mm diagonal).
The sensor's area is about 30–40% smaller than
APS-C sensors used in most other DSLRs, but still around 9 times larger than the 1/2.5" sensors typically used in
compact digital cameras. Incidentally, the imaging area of a Four Thirds sensor is almost identical to that of
110 film.
The emphasis on the 4:3
image aspect ratio sets Four Thirds apart from other DSLR systems, which usually adhere to the 3:2 aspect ratio of the traditional
35mm format
135 film, more popularly referred to as 35 mm film or 35 mm, is a format of photographic film used for still photography. It is a film with a film gauge of loaded into a standardized type of magazine – also referred to as a casse ...
. However, the standard only specifies the sensor diagonal, thus Four Thirds cameras using the standard 3:2 aspect ratio would be possible;
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
The Panasonic Lumix DMC-GH1 is a digital mirrorless interchangeable lens camera adhering to the Olympus and Panasonic developed Micro Four Thirds System (MFT) system design standard. Panasonic classified the GH1 as a hybrid stills/video camer ...
uses a multi-aspect sensor designed to maximize use of the
image circle
The image circle is the cross section of the cone of light transmitted by a lens or series of lenses onto the image plane. When this light strikes a perpendicular target such as photographic film or a digital camera sensor, it forms a circle of ...
at 4:3, 3:2, and 16:9; each ratio having a diagonal of 22.5 mm.
[.]
Sensor aspect ratio influences lens design. For example, many lenses designed by Olympus for the Four Thirds System contain internal rectangular baffles or permanently mounted "petal"
lens hood
In photography, a lens hood or lens shade is a device used on the front end of a lens to block the Sun or other light source(s) to prevent glare and lens flare. Lens hoods may also be used to protect the lens from scratches and the elements witho ...
s that optimise their operation for the 4:3 aspect ratio.
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".
[.] 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.
Advantages, disadvantages and other considerations
Advantages
*
![Olympus E-420](https://upload.wikimedia.org/wikipedia/commons/4/49/Olympus_E-420.jpg)
The smaller sensor size makes possible smaller and lighter camera bodies and lenses. In particular, the Four-Thirds system allows the development of compact, large aperture lenses. Corresponding lenses become larger, heavier and more expensive when designed for larger sensor formats.
* Telecentric optical path means that light hitting the sensor is traveling closer to perpendicular to the sensor, resulting in brighter corners, and improved off-center resolution, particularly on wide angle lenses.
* Because the flange focal distance is significantly shorter than those on Canon FD, Canon EF, Nikon F and Pentax K, lenses for many other SLR types including the old Olympus OM System can be fitted to Four Thirds cameras with simple mechanical adapter rings. Such mechanical adapter rings typically require manual setting of focus and aperture.
Disadvantages
* Compared to a larger sensor with equivalent pixel count, a Four Thirds sensor gathers disproportionately less light per pixel. Not only are the individual photosites smaller, but each loses more of its total area to support circuitry and edge shading than a larger photosite would. With less captured light to work with, each photosite requires additional amplification, with associated higher noise as well as reduced
dynamic range
Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. It is measured either as a ratio or as a base-1 ...
. A telecentric lens design can mitigate this problem, but the sensor remains more sensitive to the angle of incoming light, and has more pronounced image corner light falloff.
* The resolution of a sensor is often measured as the total sensor pixel count in
megapixels
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the smal ...
, and this is often a primary decision-making factor in choosing a camera. Smaller sensors are tougher to manufacture with the same pixel density as larger sensors, and place a greater demand on optics, since a lens must achieve greater absolute resolving power to produce an adequate picture on a smaller sensor, compared to a larger sensor of the same pixel resolution. A smaller pixel active area reduces the averaging effect and allows a better sampling of high spatial frequencies, mitigating this problem.
[.]
* To get the same
angle of view
The angle of view is the decisive variable for the visual perception of the size or projection of the size of an object.
Angle of view and perception of size
The perceived size of an object depends on the size of the image projected onto the ...
as with a larger sensor, the focal length of the lens used with a Four Thirds sensor needs to be shorter. However, to get the same
depth of field
The depth of field (DOF) is the distance between the nearest and the furthest objects that are in acceptably sharp focus in an image captured with a camera.
Factors affecting depth of field
For cameras that can only focus on one object dist ...
and light gathering capability as with a larger sensor, the lens aperture needs to be kept constant. In other words, the
focal ratio
In optics, the f-number of an optical system such as a camera lens is the ratio of the system's focal length to the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical Engineering'', 4th Ed., 2007 McGraw-Hill Pro ...
of the lens must be smaller on the Four Thirds system to give the same depth of field and image noise. Since it is more difficult to produce faster lenses (lenses with smaller focal ratios), it can be difficult or impossible to find a lens that produces as shallow a depth of field, and gathers as much light, as an equivalent lens on larger formats. For instance, a 35mm "full-frame" DSLR can match the depth of field of a Four Thirds camera by closing down the aperture by two stops; but it may be more difficult or impossible for a Four Thirds System to match the shallow depth of field of a 35mm camera using a fast lens.
Differences
* Most Four Thirds cameras (notably those manufactured by Olympus) use an aspect ratio of 4:3 rather than 3:2; newer models offer cropping to 3:2, but this results in a reduced image diagonal (i.e., the effective crop factor is then 2.08).
Four Thirds System companies
As of the 2006
Photo Marketing Association The Photo Marketing Association International (PMA) International Convention and Trade Show was an annual imaging technology trade show conducted by PMA held in Las Vegas. Since 2012, the show has been branded as PMA@CES, reflecting its reschedulin ...
Annual Convention and Trade Show, the Four Thirds consortium consisted of the following companies:
*
Fuji Fuji may refer to:
Places China
* Fuji, Xiangcheng City (付集镇), town in Xiangcheng City, Henan
Japan
* Mount Fuji, the tallest mountain in Japan
* Fuji River
* Fuji, Saga, town in Saga Prefecture
* Fuji, Shizuoka, city in Shizuoka Prefec ...
*
Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
*
Leica
*
Olympus
*
Panasonic
formerly between 1935 and 2008 and the first incarnation of between 2008 and 2022, is a major Japanese multinational corporation, multinational Conglomerate (company), conglomerate corporation, headquartered in Kadoma, Osaka, Kadoma, Osaka P ...
*
Sanyo
, stylized as SANYO, is a Japanese electronics company and formerly a member of the Fortune Global 500, ''Fortune'' Global 500 whose headquarters was located in Moriguchi, Osaka, Moriguchi, Osaka prefecture, Japan. Sanyo had over 230 subsidiari ...
*
Sigma
Sigma (; uppercase Σ, lowercase σ, lowercase in word-final position ς; grc-gre, σίγμα) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used as ...
This does not imply a commitment to end user products by each company. Historically, only Leica, Olympus, and Panasonic have produced bodies. Olympus and Leica/Panasonic have made dedicated Four Thirds lenses, and Sigma makes adapted versions of their "DC" lenses for APS-C format DSLRs. Kodak once sold sensors to Olympus for use in their Four Thirds bodies, but the newer Olympus Four Thirds cameras used Panasonic sensors.
Four Thirds System cameras
The majority of Four Thirds System cameras and Four Thirds lenses are made by Olympus. Many Four Thirds cameras use "sensor-shift" in-body
image stabilization
Image stabilization (IS) is a family of techniques that reduce blurring associated with the motion of a camera or other imaging device during exposure.
Generally, it compensates for pan and tilt (angular movement, equivalent to yaw and pit ...
, making the need for image stabilization technology in its lenses unnecessary. All Four Thirds cameras also incorporate an automatic sensor cleaning device, in which a thin glass filter in front of the sensor vibrates at 30 kHz, causing dust to fall off and adhere to a piece of sticky material below. 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. Because of the smaller format of Four Thirds, the viewfinders tend to be smaller than on comparable cameras.
Manufacture of Four Thirds cameras came to an end after the introduction of the mirrorless Micro Four Thirds format. Discontinued models include:
*
Leica Digilux 3
The Digilux 3 is a digital single-lens reflex camera introduced by Leica Camera, Leica on 14 September 2006. The Digilux 3 and the Panasonic Lumix DMC-L1 are similar specification cameras, using the Four Thirds System, Four Thirds standard lens mo ...
*
Olympus E-1
The Olympus E-1, introduced in 2003, was the first DSLR system camera designed from the ground up for digital photography This contrasts with its contemporaries which offered systems based on reused parts from previous 135 film systems, modified ...
*
Olympus E-3
*
Olympus E-5
*
Olympus E-30
The Olympus E-30 is a Four Thirds System camera produced between December 2008 and about 2011. It was the only two-digit model in the E DSLR series, positioned between the Olympus E-520
The Olympus E-520 (or Olympus EVOLT E-520 in North Ameri ...
*
Olympus E-300
The Olympus E-300 (Olympus Evolt E-300 in North America) is an 8-megapixel digital SLR manufactured by Olympus of Japan and based on the Four Thirds System. Announced at photokina 2004, it became available at the end of 2004. It was the second ...
*
Olympus E-330
The Olympus E-330 is a DSLR launched on 30 January 2006, using the Four Thirds System lens mount standard. Its main feature is its live image preview functionality, permitting an image to be previewed on the LCD screen. While live image previ ...
*
Olympus E-400
The Olympus E-400 is a digital single-lens reflex camera launched by Olympus on 14 September 2006, using the Four Thirds System lens mount standard. This 10 megapixel camera could be compared to other DSLRs unveiled during the summer of 2006 with ...
*
Olympus E-410
*
Olympus E-420
The Olympus E-420 (or Olympus EVOLT E-420 in North America) is a 10 megapixel digital single-lens reflex (DSLR) camera made by Olympus. The camera conforms to the Four Thirds System standard, and together with its siblings in the E-4XX series, ...
*
Olympus E-450
*
Olympus E-500
The Olympus E-500 (Olympus EVOLT E-500 in North America) is an 8-megapixel digital SLR camera manufactured by Olympus of Japan and based on the Four Thirds System. It was announced on 26 September 2005. Like the E-300 launched the previous year ...
*
Olympus E-510
The Olympus E-510 (or Olympus EVOLT E-510 in North America) is a 10-megapixel digital single-lens reflex (DSLR) camera oriented to the "prosumer" or "hobbyist" market.
Details
Announced in March 2007 to succeed the E-500, it represents the fi ...
*
Olympus E-520
The Olympus E-520 (or Olympus EVOLT E-520 in North America) is a 10 megapixel digital single-lens reflex (DSLR) camera.
Features
Announced in May 2008 to succeed the E-510, The E-520 adds face detection technology, auto focus live preview, wi ...
*Olympus E-600
*
Olympus E-620
The Olympus E-620 is a Four Thirds digital single-lens reflex camera from Olympus announced February 24, 2009. It combines features of the E-420 (smaller size), E-520 (image stabilization), and E-30 (new 12.3 MP sensor, slightly larger viewfi ...
*
Panasonic Lumix DMC-L1
The Lumix DMC-L1 is Panasonic's first DSLR camera, and was announced in February 2006. This camera adheres to the Four Thirds System lens mount standard, making it the first non-Olympus Four Thirds camera, and thus confirming that the Four Thirds ...
*
Panasonic Lumix DMC-L10
Four Thirds System lenses
The Four Thirds
lens mount
A lens mount is an interface – mechanical and often also electrical – between a photographic camera body and a lens. It is a feature of camera systems where the body allows interchangeable lenses, most usually the rangefinder camera, singl ...
is specified to be a
bayonet
A bayonet (from French ) is a knife, dagger, sword, or spike-shaped weapon designed to fit on the end of the muzzle of a rifle, musket or similar firearm, allowing it to be used as a spear-like weapon.Brayley, Martin, ''Bayonets: An Illustr ...
type with a
flange focal distance
For an interchangeable lens camera, the flange focal distance (FFD) (also known as the flange-to-film distance, flange focal depth, flange back distance (FBD), flange focal length (FFL), back focus or register, depending on the usage and sourc ...
of 38.67 mm.
There are currently around three dozen lenses for the Four Thirds System standard.
[.]
Before announcing that it would stop production of Four Thirds lenses in early 2017,
Olympus produced about 20 lenses for the Four Thirds System under their "
Zuiko Digital" brand. They are divided into three grades — Standard, High Grade and Super High Grade. High Grade lenses have faster maximum apertures, but are significantly more expensive and larger, and the Super High Grade zooms have constant maximum aperture over the full zoom range; all but the Standard grade are weather-sealed. Lenses within each grade cover the range from wide-angle to super telephoto.
The Zuiko Digital lenses are well regarded for their consistently good optics.
The following table lists all Zuiko Digital lenses available at the time Olympus stopped Four Thirds production:
Olympus also made 1.4× and 2×
teleconverter
A teleconverter (sometimes called tele extender) is a secondary lens mounted between a camera and a photographic lens which enlarges the central part of an image obtained by the lens. For example, a 2× teleconverter for a 35 mm camera enl ...
s and an electronically coupled
extension tube
An extension tube, sometimes also called a closeup tube or an extension ring, is used with interchangeable lenses to increase magnification. This is most often used in macro photography.
Construction
The tube contains no optical elements; it ...
.
Sigma
Sigma (; uppercase Σ, lowercase σ, lowercase in word-final position ς; grc-gre, σίγμα) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used as ...
has adapted 13 lenses for the Four Thirds System, ranging from 10 mm to 800 mm, including several for which no equivalent exists: the fast primes (30 mm and 50 mm ) and extreme telephoto (300–800 mm 5.6). As of 2014 all Sigma lenses for the Four Thirds System have been discontinued.
Leica has designed four lenses for the Four Thirds System: fast and slow normal zooms and a 14–150 mm super-zoom, all with Panasonic's image stabilization system, and an unstabilized 25 mm
prime
A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...
. These are manufactured and sold by Panasonic.
An official list of available lenses can be found on Four-Thirds.org web site.
[.]
As for the system itself, it was silently discontinued in favor of the
Micro Four Thirds System.
Micro Four Thirds System
![Olympus-MicroFT-Model](https://upload.wikimedia.org/wikipedia/commons/0/0a/Olympus-MicroFT-Model.jpg)
In August 2008, Olympus and Panasonic introduced a new format,
Micro Four Thirds.
The new system uses the same sensor, but removes the mirror box from the camera design. A
live preview
Live preview is a feature that allows a digital camera's display screen to be used as a viewfinder. This provides a means of previewing framing and other exposure before taking the photograph. In most such cameras, the preview is generated by m ...
is shown on either the camera's main
liquid-crystal display
A liquid-crystal display (LCD) is a flat-panel display
A flat-panel display (FPD) is an electronic display used to display visual content such as text or images. It is present in consumer, medical, transportation, and industrial equipmen ...
or via an
electronic viewfinder
An electronic viewfinder (EVF) is a camera viewfinder where the image captured by the lens is displayed on a small screen (usually LCD or OLED) which the photographer can look through when composing their shot. It differs from a live preview ...
, as in digital compact cameras. Autofocus may be accomplished via a
contrast detection process using the main imager, again similar to digital compact cameras. Some Olympus manufactured camera bodies also feature phase detection auto focus built into the sensor. The goal of the new system was to allow for even smaller cameras, competing directly with higher-end point-and-shoot compact digital cameras and DSLRs. The smaller
flange focal distance
For an interchangeable lens camera, the flange focal distance (FFD) (also known as the flange-to-film distance, flange focal depth, flange back distance (FBD), flange focal length (FFL), back focus or register, depending on the usage and sourc ...
allows for more compact normal and wide angle lenses. It also facilitates the use, with an adapter, of lenses based on other mounting systems, including many manual focus lenses from the seventies and eighties.
In particular, Four Thirds lenses can be used on Micro Four Thirds bodies with an adapter; however, "all of the functions of the Micro Four Thirds System may not always be available."
[Micro Four Thirds Official](_blank)
benefits list.
See also
*
Lenses for SLR and DSLR cameras
This article is about photographic lenses for single-lens reflex film cameras (SLRs) and digital single-lens reflex cameras (DSLRs). Emphasis is on modern lenses for 35 mm film SLRs and for DSLRs with sensor sizes less than or equal to 3 ...
*
Lens mount
A lens mount is an interface – mechanical and often also electrical – between a photographic camera body and a lens. It is a feature of camera systems where the body allows interchangeable lenses, most usually the rangefinder camera, singl ...
— list of lens mounts
*
Video camera tube#Size, origin of 4/3 inch sensor measurement
References
External links
Official Four Thirds System siteFour Thirds US patent 6,910,814PDF version(1.7 MiB)
nbsp;— includes a complete lens list
Four Thirds User — independent site and user-community dedicated to the Four Thirds System, including Micro Four Thirds
{{DEFAULTSORT:Four Thirds System
Lens mounts
Photography equipment
Kodak
Olympus products
Japanese inventions