Archived posting to the Leica Users Group, 2010/09/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Spot on, Frank, of course. But you mean silicon - perhaps your mind was wandering? On 9/11/10, Frank Dernie <Frank.Dernie at btinternet.com> wrote: > Hi Mark, > on the off chance your question is not rhetorical here are a few reasons > for > the difference in price between small and large sensors being much bigger > than thet between 35mm and 120 film. > Firstly the film is the same stuff, just a different shaped layer of > plastic > coated with the same light sensitive stuff. > In the case of sensors they are made on a wafer of silicone. The crystal > structure of the silicone wafer has imperfections on it, and any chip > etched > onto a part of the silicone wafer with an imperfection won't work, so it is > scrap. If, for example there is a defect every 2 inches, -all- 2 inch or > bigger chips will be scrap, so that is the biggest sensor which can be made > will be less than 2". Depending on how the layout of random faults and the > sensor layout fall on a wafer, there will be a high scrap rate even on > sensors less than 2". The scrap rate only comes down to negligible when the > sensors are -very- much less than 2". > This means big sensors are expensive since very few few of those produced > work. They are also expensive since the economy of scale is not there. Some > are made by joining 2 smaller sensors together with software to "fix" the > image at the join... > The technology for making the wafers is developing, so prices will come > down > eventually, but never to the film ratio. > > Luckily, the sensor design of small and big chips is -not- the same, unlike > film. With film, going larger format increases the potential quality by the > increase in film area less the reduction in lens quality due to the larger > image circle. Going smaller with digital the loss is -much- less than with > film since the smaller sensors are -much- finer resolution than large > sensors so the loss of quality is not nearly as much as it used to be with > film. > cheers, > Frank > > On 11 Sep, 2010, at 07:12, Mark Rabiner wrote: > >> Brownie film does not cost that much more than 35mm film. Why should >> digital? Well it does. Bummer. > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >