In article <329327a2.818700@news.uni-c.dk>, madsen@ipt.dtu.dk says...

>Can any of you give any recomandations regarding vivitar 100/3.5 macro
>and sigma 90/2.8 macro lenses.
>They will only be used occationally.

Two MF versions of the Sigma 90mm macro were excellent, as is the
achromat that comes with it to get it from 1:2 to 1:1 - it is
excellent when used on many other lenses (when stopped down).
Hope This Helps