Editing Lens mount (section)

== Notes ==
{{Cnote|A|The authoritative normative source for 4/3 standards information is Four-Thirds.Org and not 3rd-party reviews.}}

4/3's published facts:
*"Size of the 4/3-type Sensor:  The standard diagonal length of the sensor is {{Convert|21.63|mm|in}}.  It is half that of 35-mm film format ({{Convert|36|mm|in}} x {{Convert|24|mm|in}} = {{Convert|43.27|mm|in}})  The [[image circle]] of the interchangeable lens is specified based on this diagonal length. The focal length is about a half that of a 135 film camera lens assuming the same angle of view."<ref>{{cite web
| title=About Four Thirds, Standard, Whitepaper (Summary of Standard)
| publisher=[[Four Thirds System]]
| url=http://www.four-thirds.org/en/about/standard.html
| access-date=2008-08-11
| archive-url=https://web.archive.org/web/20090307060248/http://www.four-thirds.org/en/about/standard.html
| archive-date=2009-03-07
| url-status=dead
}}</ref>
*"The foundation for the high picture quality of the Four Thirds system is the lens mount, which is about twice the diameter of the image circle."<ref>{{cite web
| title=About Four Thirds, Standard, Benefits of Four Thirds
| publisher=[[Four Thirds System]]
| url=http://www.four-thirds.org/en/about/benefit.html
| access-date=2008-08-11
}}</ref>
*"Differences between Four Thirds System mount and Micro Four Thirds System mount:   Mount diameter reduction; As a result of research aimed at facilitating the design of compact, lightweight lenses while maintaining the current strength, the outer diameter of the lens mount has been reduced by approx. {{Convert|6|mm|in}}. ... the Micro Four Thirds System ... specifies the optimum flange back length required to reduce camera size and thickness, assuming the omission of the mirror box.  The flange back length has been reduced to about 1/2 that of the Four Thirds System."<ref>{{cite web
| title=Micro Four Thirds, Standard, Whitepaper (Summary of Standard)
| publisher=[[Four Thirds System]]
| url=http://www.four-thirds.org/en/microft/whitepaper.html
| access-date=2008-08-11
}}</ref>

So:
*21.63mm * 2 = {{Convert|43.26|mm|in}} or ~44mm
*43.26mm – 6mm = {{Convert|37.26|mm|in}} or ~38mm
*<math>\mathrm{(21.63\ mm)^2 = 17.3\ mm ^ 2 + 12.98\ mm ^ 2}</math>;  See: [[Pythagorean theorem]] (<math>5^2 = 4^2 + 3^2</math>)

NOTE:
Some published reviews of 4/3 instead cite the (female) "outside diameter" of the lens or mount as ~50mm (and micro-4/3 as ~44mm),<ref name=dpr>{{cite web
| title = Olympus and Panasonic announce Micro Four Thirds
| publisher = Digital Photography Review
| url = http://www.dpreview.com/news/0808/08080501microfourthirds.asp
}}</ref> and not the appropriate ''major'' diameter (D) ~44mm which is the camera body's female mount inside-diameter and the lens's male mount outside-diameter (micro-4/3 ~38mm).
<!-- end of Cnote A -->