In article <31C011AD.7B87@students.wisc.edu>, mkackman@students.wisc.edu says...

>I'm considering buying an inexpensive AI MF prime lens in the 100mm
>range. The Series E 2.8/100 and the 2.8/135 are both fairly highly
>rated, especially for the price. Any further comments about either of
>these lenses? The lens will be used with my FG for a variety of uses --
>portraits, various exteriors, etc.
>Alternatively, I would also be interested in a macro lens of similar
>quality/price. Is the Sigma 2.8/90 any good?

All of the lenses you mentioned are excellent, even at wider apertures.
Hope This Helps