Sigma 80-400 Focus Past Infinity
Is it unusual for a lens to focus past infinity?? My new Sigma 80-400 does not stop at the infinity mark on the lens barrel but goes past it. I had to send the lens in for service for another matter but this wasn't addressed and I am just wondering if it is normal. I've never seen it before...but that doesn't mean squat.
Ray Larson
Nikon D80, D300, D700 all gripped, Nikkor 50 f1.8 Nikkor 18-200 VR Nikkor 70-200 VR f2.8 Nikkor 28-300 VR, Sigma 50-150 f2.8 Sigma 80-400 OS Sigma 150-500 OS Nikon SB600
Nikon D80, D300, D700 all gripped, Nikkor 50 f1.8 Nikkor 18-200 VR Nikkor 70-200 VR f2.8 Nikkor 28-300 VR, Sigma 50-150 f2.8 Sigma 80-400 OS Sigma 150-500 OS Nikon SB600
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It is not unusual to see lenses, especially long lenses and lenses with "exotic" elements, with focus capabilities beyond infinity.
The usual reason is to allow the lens to focus even at elevated temperatures, which causes the lens barrel to expand and most of that expansion is along the length of the lens.
Lenses that are designed for visible light and UV applications also need to allow for extra length because UV will focus infinity at a greater distance from the image plane. (IR focuses at a closer distance to the image plane than visible spectrum light.)
Moderator of the Cameras and Accessories forums
I assumed that there was a reason...just never seen it on any other lenses I have worked with.
Nikon D80, D300, D700 all gripped, Nikkor 50 f1.8 Nikkor 18-200 VR Nikkor 70-200 VR f2.8 Nikkor 28-300 VR, Sigma 50-150 f2.8 Sigma 80-400 OS Sigma 150-500 OS Nikon SB600