> In a message dated 10/1/98 8:14:20 AM Eastern Daylight Time,
> Perry.Mitchell@btinternet.com writes:
>
> > 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
>
> <><><><><><><><><><><><><><><>
>
> 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
Moovy makes a good point. These problems vary widely from one unit to another,
even of the same model. Question: How many of us are ever in a situation where we
get to evaluate the actual unit we will get before we buy? Don't you wish....
--
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