Archived posting to the Leica Users Group, 2006/03/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>"4/3" refers to the aspect ratio Not only: The name of the system comes from the size of the imaging sensor. The sensor used is a "4/3 inch" type sensor. The length is based on the diameter of a particular size of Vidicon tube ? the actual light sensitive area being smaller. It is sometimes stated that the name refers to the 4:3 aspect ratio of the sensor used in current cameras. The long side of the rectangular photographs that Four Thirds cameras produce is 4/3 (1.33 times) the size of the short side. This places it between the usual 35 mm format (with an aspect ratio of 1.5) and a square (which has an aspect ratio of 1.0). There is little doubt that 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 in this article, is quite 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 ..." Additionally, it is necessary to know the aspect ratio in order to design lenses. Indeed, many lenses designed by Olympus for the four thirds system contain internal rectangular baffles or permanently mounted "petal" lens hoods that restrict the lenses to operation only with the 4:3 aspect ratio. More at http://en.wikipedia.org/wiki/Four_Thirds_System