"Dok" <harleydok@hotmail.com> wrote in message news:13f90950.0312310717.110260e7@posting.google.com...

> I've got the Nikon 85mm/1.8 AF-D that I use with my N70. When the

> subjuct is centrally located, the focus is right on. However, when I

> focus and then then recompose following the rule of thirds, I've

> noticed that my subject is somewhat blurred. At first I thought it

> was me but I've done this on a tripod and get the same result. I've

> not tried to photograph newsprint or lines to see if there is any

> change as you move across the lens field.

>

> Is this expected with a telephoto lens or do I have a bad case of

> spherical aberration? Good bokeh with incorrect use of this lens?

This lens is better than most at all focus distances even wide-open,

assuming you have a good-average sample (lens samples do vary,

and should be checked and returned if defective...). Others have

suggested focusing manually after composition, but the viewfinder

on this (and the N90) are softer than the excellent ones on most

Nikons, making accurate MF more difficult. If you are shooting

close and focusing, then rotating the camera, you are (by simple

geometry) changing the camera-focus distance, introducing focus

errors - which is why I prefer MF focus (you can focus properly

over most of a good VF frame and reduce the effects of

rotation errors [though there are other issues with newer camera

VFs used off center for focus, alas - and the brightening optics

can give you false focus away from the center...]). Stopping

down some will help cover the focus errors, but this is not ideal...

--

David Ruether

d_ruether@hotmail.com

http://www.David-Ruether-Photography.com