----- Original Message ----- From: "keller.schaefer" Subject: AW: viewfinder magnification
> Hmm - I agree with all you are saying, except for the tolerances. The ME > Super mirror box that I am looking at right now is a cast aluminium part. It > attaches to the body, to the mount and to the prism. If it is only machined > to *standard* engineering tolerances of 0.1 mm then it will easily position > the screen frame within +/- 0.2 mm of the film window (or relative to the > sensor) and that is all that is needed to reasonably center any frame size > (+/- 1 mm would be really awfull). > A 100% sized screen set off by 0.2 mm in one direction would still show > about 99.4% of the true image. It's not just positioning of the screen that's important. The lens mount also has to be in perfect registration, and the camera has to be solidly enough built to keep it that way. The mirror alignment is critical, and cannot shift it's rest position at all over some tens of thousand of exposures. The prism must be precisely aligned as well as the viewfinder elements. In order to build a camera with a 100% accurate viewfinder, you cannot use modern assembly line techniques. You are back to the old school of bench building each camera individually past a certain point. 100% accurate means just that. There is no allowable slop in the build. That means shimming each composnet of the viewing system in peice by peice and ensuring that perfect alignment is maintainted. This may not be an especially difficult task, but it is a time consuming one, and ensures that the camera in question will not be a mass produced item. It also ensures that the product will be substantially more expensive than the same camera without the 100% viewfinder. William Robb
