55-200 Focus Past Infinity.

[bowthing]

I was shooting at "infinity" with the 55-200 this evening, and I got tired of autofocusing so I switched to manual.  My subject was a mountain 33 miles away.  I got a lot of out-of-focus shots because the lens will focus PAST infinity in manual (unless 32 miles is not infinity yet!).  Didn't know this.  Beware...

 

I haven't tried my other lenses.

[JaapD]

I have seen this on many other lenses, including my Canon 70-200 f/2.8. This has to do with tolerances in the design, mostly temperature related aspects. You always need to be able to focus at infinity, over the complete temperature range between the extreme cold and heat. In order to guarantee this the lens is designed in such a way to mechanically focus beyond infinity. So there is nothing wrong with your lens.

[Aswald]

I agree with JaapD.

 

I first noticed this with older Canon FD manual focus lenses years back. Canon told me then that extreme temperatures affect lenses especially focus. Different at different focal lengths especially on a zoom.

[frod]

I believe it's also so that AF can focus past infinity so that it can determine the focus point without the motor continually hitting a hard stop.

[bowthing]

Thanks, guys!  Those answers all make perfect sense.  On my old film cameras I just remember setting to the hard stop for infinity.  They probably weren't in perfect focus all the time!

Edited March 18, 2016 by bowthing