> Several posters are getting in real deep with the XL-1 focus mechanism.
> There seems to be some suggestion that lenses with an internal focus
> mechanism cannot track whilst zooming - this is piffle!
> My broadcast Canon 8 x 6 and many of its modern cousins and rivals often
> use internal focus so that the lens front element is static and can
> mount a filter holder.
> Perry Mitchell
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There must be something wrong with my VX1K, because it seems to track for
backfocus just fine. (Test Method: Shoot an object at about 15 or 20 feet
away---not at infinity. Use low light so you have a relatively wide iris.
Zoom in. Focus manually. Zoom out and note the focus changes, if any, along
the way as well as the state of focus at the full wide point.)
Tracking tests provide a curve of focus error versus focal length. It's
usually a shallow "S" curve, even for the most expensive lenses.
My VX1K does a very nice job of tracking. Not absolutely perfect, but very
nice. Maybe there's a lot of variability in manufacture. Microscopic
differences in assembly tolerances might make the diff...
Since the autofocus is fast and accurate and doesn't "hunt" very badly, I
use it in rapidly-changing situations ---like football. I use manual
vurtually everywhere else. Works perfect.
bb
s1