Hi--

> Tonight I used my Nikkor 24-120 for portrait photography, and I
>noticed that however I manually
>set the aperture on the lens, it still changes by a full stop when I
>zoom in on the subject. Any reason why
>the lens does this?

Um, yes...., it is a variable-aperture lens....;-)
(F3.5 at 24mm, f5.6 at 120, a 1.3-stop shift at all stops,
though with illumination variation, and with the showing of
only the nearest 1/3 stop, you may not see the whole 1.3-stop
shift with zooming...)