Focusing zoom lenses

[tom beard]

On my old Canon F1 SLR I had a 70-200mm non automatic zoom lens. It was standard practice to focus the lens fully zoomed out (200mm), then pull back to frame the shot (say 100mm). I now have two Nikkor kit lenses (18-105 and 70-300) on a D-90 body. When setting up a shot I find myself manually focusing these lenses the same way out of old habit even when using auto focus. Do the same techniques apply with the new auto focus lenses? Focusing this way seems to come in handy especially when using spot metering. Any advice will be appreciated.

Thanks, Tom Beard

 

[IgsEMT]

if you MF then as long as you get it...
in AF, it depends how your AF is set. If continues focus then recomposing the shot will also change the focusing point(s), if you lock the focus then recompose it'll work as well.
The only purpose to zoom in and focus is to make sure that your subject is sharp.
Now I'll raise some hell I'm holding now D90 and D300s with 18-105 lens (of which you speak of) and 17-55 2.8 Under crappy lighting (and i've experimented with this on the job as well) 18-105 focuses faster then 17-55, at least in the situations that I've been under. BIG SURPRISE FOR ME.

 

[tom beard]

IgsEMT, Thanks. I guess old habits die hard and it really doesn't matter. That's strange about your 17-55 2.8 focusing slower than a kit lens. I have that lens on my list for better bokeh. May be Kim H knows what's going on. Tom

 

[IgsEMT]

Maybe he does
I'm just happy I didn't pay for the lens, I burrowed it from a buddy of mine.