> 4. Poorly positioned mirror (the usual problem) will have no > effect on film focus, but will affect focus screen focus.
Actually, Bob, mirror misalignment ~will~ affect film focus, albeit indirectly. (However, directly or indirectly, the effect is going to be that the image cast onto the film will not be sharp.) Since the user will be focusing the lens so as to make the focus screen image as sharp as possible, if the mirror is out of alignment, he/she will always be setting the lens so as to cause the image landing on the film plane to be out of focus. (A pentaprism SLR always makes the assumption that the mirror focus is aligned with the film plane focus - if they don't match, then out-of-focus images will be captured at the film plane.) Therefore, a poorly positioned mirror ~will~ have an effect on film focus. Fred - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
