Archived posting to the Leica Users Group, 2006/03/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I don't believe any of the hoods are permanently mounted, Didier, but then there are one or two of the lenses I have yet to examine closely. On 3/21/06 11:40 AM, "Didier Ludwig" <rangefinder@screengang.com> wrote: > > >> "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 > > > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information