An 8mm fisheye will form a circular image centered on 35mm film. A 16mm
fisheye will form a cirucular image with the edges of the circle at the
corners of the 35mm film. The image will have a rectangular shape because it
is larger than the film.
A fisheye is a lens which has intentional "barrel distortion". (It tries to
preserve angular area vs. a rectilinear lens which stretches the image at
the edges) Focal length doesn't have anything to do with whether it is a
fisheye lens or not.
Example; the 7-14mm digital Zuiko is a rectilinear lens. The 8mm digital
Zuiko is a fisheye lens.
-jeff
>From: Dan Mitchell <danmitchell@xxxxxxxx>
>
> Poking around on the bay for fisheye lenses, I find one place selling
>two different things:
>
> item 7563223184 is a 8mm/f3.5, which is what I'd expect a fisheye to be.
>
> but what, then, is item 7563223339 ? It's apparently 16mm/2.8 fisheye
>-- but how can that also be a fisheye if the 8mm lens was? Is fisheye
>just "not rectilinear"? And also the auctions claim that the 16mm one
>has a 180 degree FOV, and also that the 8mm one has a 180 degree FOV.
>I'm confused -- what's going on here?
>
> -- dan
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