In article <6g58v9$lru$1@nnrp1.dejanews.com>, evansc01@btinternet.com says...

>I am currently trying to purchase a wide angle zoom manual focus for a Nikon.
>I cannot afford a Nikkor lens so I am looking at various independent lens
>manufacturers. Given that a lens is essentially a scientific instrument for
>focussing an image, does any know of a site or paper source where a
>technical, rather than personal, evaluation of such lenses is made?

Hmmm, two issues...
Regarding the first, I would recommend the really excellent 20mm
f2.8 Nikkor (or the 24mm, if you don't want to go that wide), since
the price (maybe used...) would be roughly the same as a third or
fourth-rate "3rd-party" WA zoom (they ALL are pretty poor, if you
are at all critical of their image quality....), and WA zooms are
far less useful than tele zooms, since your feet are far more
effective with wides than teles for changing subject coverage.
Regarding the second, a really useful "scientific" evaluation of
a lens would fill a book, and be totally useless for most people.
The simplified versions one sees in "test reports" tend to be
misleading for various reasons (I may be covering that soon...;-),
and I would sooner trust an experienced user's evaluation than
misbegotten solid-looking numbers...;-)
David Ruether
http://www.fcinet.com/ruether