Four Thirds System
470685
225555268
2008-07-14T08:15:47Z
Ashley Pomeroy
128005
/* Sensor size and aspect ratio */ Made the caption even more bitchin'
[[Image:4 3logo.png|thumb|right|Four Thirds logo]]
The '''Four Thirds System''' is a standard created by [[Olympus Corporation|Olympus]] and [[Kodak]] for [[digital single-lens reflex camera]] (DSLR) design and development.<ref name='DPReview.com 2001-02-13'>{{cite news | first= | last= | coauthors= | title=Kodak and Olympus join forces | date=[[2001-02-13]] | publisher=Amazon.com | url =http://www.dpreview.com/news/0102/01021301kodakolympus.asp | work =DPReview.com | pages = | accessdate = 2007-11-07 | language = }}</ref> (Four Thirds is a registered trademark of Olympus Optical Co., Ltd.)
The system provides a [[Standardization|standard]] that, with [[digital camera]]s and [[Lenses for SLR and DSLR cameras|lenses]] available from multiple manufacturers, allows for the interchange of lenses and bodies from different [[manufacturer]]s. {{US patent|6910814}} seems to cover the standard. Four Thirds is not an [[open standard]], however, as it does not meet the "allowing anyone to use" criterion commonly accepted as the definition of an open standard.{{Fact|2007-07-28|date=July 2007}}<!-- What is required to use it? -->
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 lens|telecentric]] designs. The size of the sensor is slightly smaller than for most DSLRs (see drawing below) 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 [[135 film|35 mm film]] standard, and is correspondingly more compact. In common terms the Four Thirds System is said to have a focal length [[Crop factor#Magnification factor|magnification factor]] of exactly 2. Although use of this terminology is debatable because the Four Thirds System is not based upon 35 mm standards, stating focal lengths in [[35 mm equivalent focal length]] is normal in the [[digital camera]] industry.
== Sensor size and aspect ratio ==
[[Image:SensorSizes.png|thumb|right|Drawing showing the relative sizes of sensors used in most current digital cameras, relative to a [[135 film|35mm film]] frame.]]
The name of the system comes from the size type of the image sensor used in the cameras. The image sensor 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]]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" diameter.
The size of the sensor is 18×13.5 mm (22.5 mm diagonal), with an imaging area of 17.3×13.0 mm (21.6 mm diagonal).<ref name='Olympus-Europe 4/3'> {{cite web|url=http://www.olympus-europa.com/consumer/dslr_7045.htm |title=No more compromises: The Four Thirds Standard |accessdate=2007-11-09 |work=Olympus Europe }}</ref> Its area is 30–40% less than the [[APS-C]] sensors used in most other DSLRs, but around 9 times larger than the 1/2.5" sensors typically used in [[compact digital camera]]s (see [[image sensor format]]).
The Four Thirds system uses a 4:3 [[Aspect ratio (image)|image aspect ratio]], in common with compact digital cameras. This differs from other DSLRs which usually adhere to the 3:2 aspect ratio of the traditional [[135 film|35 mm]] format. 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) is 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…"
A major reason to choose 4:3 for the sensor proportions is that it has historically been the standard for [[television]] and became a dominant aspect ratio for computer monitors, as found in the [[VGA]], [[SVGA]], [[XGA]], [[SXGA+]], [[UXGA]] and [[QXGA]] standards.
Sensor aspect ratio has an impact on lens design. 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.
John Knaur, a Senior Product Manager at Olympus, states that "The FourThirds refers to both the size of the imager and the aspect ratio of the sensor".<ref name = "Knaur">[http://web.archive.org/web/20021205033057/http://www.a-digital-eye.com/Olympus43Q&A.html Knaur] Interview October 01, 2002.</ref> He goes on to state the similarity between 4:3 and the standard printing size of 8×10, as well as medium format 6×4.5 and 6×7 cameras.
== Mechanical considerations ==
The Four Thirds [[lens mount]] is specified to be a bayonet type with a [[flange focal distance]] of 38.67 mm.
== Advantages, disadvantages and other factors ==
===Advantages===
* The smaller sensor size makes possible smaller and lighter camera bodies and lenses. In particular, the potential exists for very fast lenses and very high quality lenses at lower costs. Currently this is evident to some extent in the Olympus E-400, E-410 and E-420 bodies and their kit lenses, and in longer telephoto lenses.
* Telecentric optical path means that light hitting the sensor is traveling perpendicular to the sensor, resulting in brighter corners, and most importantly improved off center resolution, particularly on wide angle lenses.
* Because the flange focal distance is significantly shorter than most competing mounts (such as Canon FD, Canon EF, Nikon F and Pentax K), lenses for many other SLR types can be fitted to Four Thirds cameras with simple mechanical adapter rings. (Such mechanical adapter rings typically require manual setting of focus and aperture.)
* Although in no way related to the Four Thirds standard in itself, there is the current advantage that all Four Thirds cameras have the Olympus [[Supersonic Wave Filter]] (SSWF) dust reduction system, generally regarded to be the best dust reduction system available. (See article [[dust reduction system]] for details.)
===Disadvantages===
* Smaller sensors are generally more prone to [[image noise|noise]]. Noise typically becomes more pronounced at high [[Film speed|ISO]] exposures, meaning that picture quality may suffer in low light situations where the ISO has to be increased above 400.<ref>{{cite web| date =February, 2008| title =Olympus E-3 Review, February 2008, Simon Joinson| publisher =Digital Photography Review|url=http://www.dpreview.com/reviews/olympuse3/|accessdate =2008-02-22}}</ref>
* There are not as many lenses available as there are for some of the competing DSLR systems. (As mentioned above, lenses for competing systems can usually be mounted using an adaptor, but with the loss of auto-focus and with the need to manually set the aperture. Note that this is not an intrinsic disadvantage of the Four Thirds System, and the situation could change in the future. In-body image stabilization on the E-510, E-3 and E-520 can be used with non-Four Thirds System lenses.<ref>{{cite web |date=May, 2008 |title=Retro lens focus in new Olympus firmware, January 2008| publisher=Digital Photography Review|url=http://www.dpreview.com/news/0801/08012912olympuse3e510fw.asp |accessdate=2008-05-21}}</ref>)
* Telecentric optical path means more aggressive retrofocus design for wide lenses, which makes them bigger and difficult to have big apertures.
===Other factors===
The following two factors can be considered to be advantages under certain circumstances and disadvantages under other circumstances.
* The smaller sensor means that the [[depth of field]] is greater than for cameras with a larger sensor. See [[depth of field#DOF vs. format size|depth of field: DOF vs. format size]] for a discussion of this aspect. Compared to a 35mm or [[Full-frame digital SLR|full frame]] camera the depth of field is approximately twice as great. Compared to most other DSLR cameras that use [[APS-C|APS-C size sensors]] the depth of field for a Four Thirds camera is approximately 25% greater.
:Whether this greater depth of field is an advantage or disadvantage depends on the desired effect. For taking portraits or other pictures where the subject is to be isolated from the background (by blurring the background) it is a disadvantage. For landscape, telephoto and macro photography, and most point-and-shoot photography, it is an advantage.
* The aspect ratio of pictures taken with a Four Thirds camera is 4:3, while all other DSLR cameras and full frame 35mm film cameras take pictures with an aspect ratio of 3:2. Nearly all compact digital cameras take pictures with a 4:3 aspect ratio.
: For traditional print and frame sizes that have an aspect ratio of 3:2 (6×4", 9×6", 12×8") this is a disadvantage for Four Thirds cameras as photographs will have to be cropped or printed with borders to fit these sizes. The same applies if the picture is to be used for a wide-screen application.
: Some other traditional print sizes (5×7", 8×10", 11×14") are closer to a 4:3 aspect ratio than they are the 3:2 aspect ratio, meaning the photographer does not need to crop as much or have large matting to meet these sizes. The same applies for pictures to be used on standard PC screens and non-HDTV television screens.
== 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 [[alphabet]]ical [[Collation|order]]):
* [[Fujifilm|Fuji]]
* [[Eastman Kodak|Kodak]]
* [[Leica Camera|Leica]]
* [[Olympus (company)|Olympus]]
* [[Matsushita|Panasonic]]
* [[Sanyo]]
* [[Sigma Corporation|Sigma]]
This should not be interpreted as a commitment to end user products by each company. Up to now, only Leica, Olympus and Panasonic have bodies, and Leica, Olympus and Sigma have lenses in the market. Kodak, for example, has sensors to sell to body makers.
== Four Thirds System cameras ==
* [[Olympus E-1]] (November 2003)
* [[Olympus E-300]] (December 2004)
* [[Olympus E-500]] (September 2005)
* [[Olympus E-330]] (January 2006)
* [[Panasonic Lumix DMC-L1]] (February 2006)
* [[Leica Digilux 3]] (September 2006)
* [[Olympus E-400]] (September 2006)
* [[Olympus E-410]] (April 2007)
* [[Olympus E-510]] (June 2007)
* [[Panasonic Lumix DMC-L10]] (October 2007)
* [[Olympus E-3]] (November 2007)
* [[Olympus E-420]] (May 2008)
* [[Olympus E-520]] (June 2008)
== Four Thirds System lenses ==
[[Image:FourLenses.jpg|thumb|300px|right|Four lenses for the Four Thirds System. These are three Olympus zooms (40–150 mm, 11–22 mm and 14–54 mm) and a Sigma prime (30 mm).]]
There are currently around three dozen lenses for the Four Thirds System standard.<ref name = "Wrotniak">[http://www.wrotniak.net/photo/oly-e/lenses.html Wrotniak] lens list.</ref>
* [[Olympus (company)|Olympus]] has announced a total of 20 lenses for the Four Thirds System, including a couple not yet released and a couple superseded by newer models. Focal lengths range from 7 to 300 mm (14–600 mm in [[35 mm equivalent focal length]]), and include macros.<ref name='Oly lens roadmap'> {{cite web|url=http://www.olympus.co.uk/consumer/images/E-System_Lens_Roadmap.pdf |title=Olympus E-System Zuiko Digital Interchangeable Lens Roadmap |accessdate=2007-11-29 |publisher=Olympus UK }}</ref>
* [[Sigma Corporation|Sigma]] has adapted 12 lenses for the Four Thirds System, ranging from 18 to 800 mm.
* [[Leica Camera|Leica]] has made 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 {{f/|1.4|link=yes}} 25 mm [[prime lens|prime]].
== References ==
<references />
== See also ==
*[[Digital single-lens reflex camera]]
*[[Lenses for SLR and DSLR cameras]]
*[[Lens mount]]
*[[List of lens mounts]]
==External links==
*[http://www.four-thirds.org Official Four Thirds System] site.
*[http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=6910814 Four Thirds US patent 6,910,814]; [http://www.pat2pdf.org/patents/pat6910814.pdf PDF version] (1.7 MiB)
*[http://www.wrotniak.net/photo/oly-e/index.html Andrzej Wrotniak's pages about the Four Thirds System] include a complete lens list.
*[http://fourthirdsphoto.com Fourthirdsphoto.com] Site for Four Thirds System users.
*[http://www.fourthirds-user.com Four Thirds User] Site for Four Thirds System users.
*[http://www.flickr.com/groups/4-3rd/ Flickr Group For Four Thirds] Flickr Group for Four Thirds
*[http://www.4-3system.com/ 4-3system.com] News and reference site
*[http://four-thirds-lenses.com/ Four Thirds Lenses.com] Blog with all the lenses and cameras. User reviews
*[http://reviews.slr.gr/ 4-3 equipment reviews] Reviews for SLR and lenses of 4/3
*[http://www.ftna.es Foro hispano del formato Cuatro Tercios] Forum in spanish about the Four Thirds system.
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