SGinNorcal wrote:
If you want to get technical, "beyond infinity" is the same as infinity. I paid attention to my 9th grade math teacher.
Which is why I always put 'beyond infinity' in quotes. Technically you are reducing the distance between the nodal point of the lens from the recording medium to less than the focal length. Phraseology introduced with lenses with aspheric and other exotic glass elements which are susceptible to a change in focal length affected by temperature. So the focussing helical has to mallow movement beyond the marked infinity which is engraved for a 'normal' temperature range. M ost lenses are not significantly affected by temperature variation, in my MF 'collection' the only lens I ever have had (and still have) is a Nikkor 180mm f/2.8 AiS.
AF mechanisms have to do it to allow the system to go beyond any point of focus and return to a sharpest point arrived at by going backwards and forwards till 'focus' is achieved. My early Nikon af, F 801, will hunt backwards and forwards 'forever' given a low contrast subject.
