Archived posting to the Leica Users Group, 1997/07/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>If I understand it correctly the Contax way of doing autofocus is >suboptimal. Meaning that one achieves better optical performance >if in focusing the relative positions of the elements in the lens >are changed instead of just changing the distance of the whole lens >from the film plane. Leica is all for the ultimate optical performance, >in R anyway. Why would they go for the Contax solution? This is only true if the lens uses "floating elements." Mainly zooms and over-200mm lenses, and maybe some lenses with aspherical surfaces, use floating elements, although there are exceptions. Some AF lenses focus with floating elements for purely practical reasons, especially if they are large or heavy; it's faster and easier to move a few lens elements internally with a little motor than to move the whole lens with a big motor. Most manual focus prime lenses focus by moving the whole lens closer or farther away from the film plane, so there is no difference between what the Contax AX does and the way the lens focuses normally. - - Paul