In article <4pnrb8$hr7@acmez.gatech.edu>, ccastcr@prism.gatech.edu says...

>I found a sigma 8mm lense for sale... anyone out there have any
>experience with it? I am shopping around for a good fisheye, and
>I have several options.

The sample I have is excellent, though it is definitely a bit
shy of 180 degrees in coverage, unlike the Nikkor 8mm. The Sigma
appears to perform better in color than B&W, especially at the
edge of coverage, which is a fairly clean circle (the Nikkor
often shows artifacts at the [larger] circle edge). The Nikkor
is a bit better at optimum apertures, especially in B&W, but the
Sigma is better at wide apertures (in color), which is useful for
hand-held interior photos (sharp 1/2 second HH exposures are easy,
and sharp 1 second hand-held exposures are possible!). The Sigma
is compact and light (unlike the Nikkor!). It performs reasonably
well on the Nikkor TC14A converter around f8 for VERY wide
coverage with larger image details on the film (I use it this
way for architectural documentation in tight quarters, or to
show site land-level variations over a wide area).
It can be a good lens.
Hope This Helps