----- Original Message -----
From: Ken Durling <[EMAIL PROTECTED]>
>
> Hey I just got my new 28-135, and I'm having way too much fun
> experimenting with it! I'm noticing something it does, though, that
> the 28-90 didn't do: if I switch focus from a near object to a
> farther one, either by re-aiming the lens or by switching focus
> points, the focal length also changes. It zooms in, or gets longer
> for far objects, and zooms out for near ones....
>
Hi Ken,
I believe it has someting to do with IF (internal focusing) feature of this
lens, or lenses wich had focusing groups or focusing elements inside the
lens barrel. I notice this phenomenon on several lenses which I own (or
previously owned) such as EF 24-85/3.5-5.6 USM or Tamron 28-200/3.8-5.6 LD
IF.
I remember pop photo magazine had the article which discussing this
(actually, it discussing Tamron 28-200 design and feature) about 1 or 2
years ago.
regards,,, Bambang.
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