Archived posting to the Leica Users Group, 1997/11/04
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 09:09 PM 11/4/97 -0800, you wrote: >At 10:11 PM 11/4/97 -0500, you wrote: >>I noticed that infinity is not infinity when used with the 2x APO extender. >>Atlanta's skyline is over 20 miles from Stone Mountain. The picture was >>tack sharp when the distance indicator was on 300 feet. >>Even when used without the extender infinity is not exactly at the >>'mechanical end' of the lens. Perhaps 1 to 2 mm from the end to be tack >>sharp. >> >>Is that something to worry? >> >>Regards Jorg >> > >No. This is normal and proper. You see, there is no such thing as infinity. >It's beyond the farthest possible object. Telephoto lenses frequently focus >beyond what you might perceive as infinity. That mountain range over there. >If you stop and think about it, it makes perfect sense. > >Jim > Adding to this, when focussing on distant objects (such as the moon) with long and very long lenses, you still need to be able to focus *past* the object and then come back to it. Just like focussing on a person, or car, or whatever. The process of focussing usually entails focussing past, then before, then on to the object. With telephotos, this is *way* out there. Therefore, focussing past what you perceive as infinity, is proper. Jim