some buying advice please

[Franglais]

Im slightly confused. so, you cant AF and then MF to make adjustments on Nikons?

With AF lenses the lens is mechanically linked to the autofocus motor and in order to focus manually you have to switch to "M" focus (on the camera body) which disconnects the mechanical linkage. I don't find manual focussing on an AF body+lens very easy - the focus ring is too light and there are no optical aids in the viewfinder to help you judge if you're in focus (except the green focus-OK light)

With low-end AF-S lenses (like the 18-55 non VR) if you want to retouch focus then you have to switch to M before you can turn the focus ring

With the other AF-S lenses (including the 18-105VR, 35mm f1.8DX, 18-70, 18-200, etc) you just touch the focus ring and refocus. The camera stops trying to do autofocus until you remove your finger from the shutter release and then put it back.

In reality this is not a big deal. When I want to focus on a precise spot I do the same thing as on the Leica. I switch to focussing on the center focus point (the most accurate), reframe to put the center spot on the point I want to have in focus, lightly depress the shutter release to focus and hold focus then reframe (without zooming) ready to do the shot. It only takes an instant and I redo it any time the subject moves or if I change the zoom.

[Grandpaw]

In reality this is not a big deal. When I want to focus on a precise spot I do the same thing as on the Leica. I switch to focusing on the center focus point (the most accurate), re frame to put the center spot on the point I want to have in focus, lightly depress the shutter release to focus and hold focus then re frame (without zooming) ready to do the shot. It only takes an instant and I redo it any time the subject moves or if I change the zoom.

I do this all the time and it works well but I just want to add that your camera needs to be off continuous focus and on single focus for this to work, Jeff

[OldClicker]

I switch to focussing on the center focus point (the most accurate), reframe to put the center spot on the point I want to have in focus, lightly depress the shutter release to focus and hold focus then reframe (without zooming) ready to do the shot. It only takes an instant and I redo it any time the subject moves or if I change the zoom.

I think we all use this technique, but those using a shallow DoF do have to be aware of the change in the plane of focus that can be significant when reframing. - TF