I am a mountaineer and photographer, and have always wondered if my autofocus was as accurate at high elevations as it is at sea level. Can I use Spyder LensCal to check, and ideally correct, this?
Yes, if you feel that less dense air causes differential in your autofocus, you could certainly check that with Spyder LensCal, by shooting the target both at sea-level, then again at high altitude, and determining that the focal range is the same in both conditions. However, current camera firmware only offers one slot per lens for autofocus corrections. So you would have to take Spyder LensCal with you, and adjust your lenses at altitude, then again after the climb for low level usage, unless you are willing to duplicate equipment.