Archived posting to the Leica Users Group, 1998/07/06
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]According to Leica, for a lens, infinity is (in miles) three miles away. Your rangefinder should line up and the lens be at the infinity stop (Leica M and normal M lenses) for anything three miles away or more. On an R camera, there are many long lenses that go well past infinity. My 350 goes 1/2 inch past the infinity mark. Look at a measure. One half inch is a long way. That is so you can focus properly on objects three miles and farther away. Such as the moon. With the 350 plus 2x extender (700mm) this added focus space is indeed necessary. Focusing on a ground glass requires that you go past sharp focus, come back past focus again, then back into sharp focus. Repeat as many times as necessary. This is yo-yo focusing, which is the proper method for focusing on a ground glass. Long lenses need space beyond the infinity stop in order for you to properly focus on far away objects. Some say, and I indeed believe them, that focus on long lenses will change with temperature. But I guarantee you that the hot/cold focus shift does not take up one half inch of focus space after the infinity mark. It's there so you *can* focus on far away objects. Not to accommodate a temperature shift. This is probably more than you asked for... Jim At 08:51 AM 7/6/98 -0700, you wrote: >Now my question is: where is infinity? At the farthest point on the barrel >to which you can rack the lens, or in the middle of the infinity sign, or >at the end of the infinity sign? > >Francesco >