>Actually, Nikon made 4 mirror-up fish-eyes. Here's some information
>which is based upon several books I have that describe Nikon
>stuff.
>
>6 mm F5.6 manufactured from 1/69 to 3/78 with about 4,000
> units produced.
>7.5 mm F5.6 manufactured from 10/65 to 2/70 with about 2,200
> units produced
>8 mm F8.0 manufactured from 7/62 to 4/65 unknown units
> produced
>10 mm F5.6 manufactured from 7/68 to 8/76 with about 10,000
> units produced
>
>These were all 180 deg true fish eyes, except for the 6 mm, which
>had a 220 deg view. The image circles on all of them are 23 mm
>for the 8 mm and 7.5 mm, 20 for the 10 mm, and 21.6 mm for the
>6 mm.
>
>The 10 mm is called and orthographic projection lens; the result
>is that the middle areas are larger and the sides are smaller.
>
>I've been looking for the 6 and 10 mm for about 2 years. I've
>seen the 10 for sale twice but I've been too late to buy it.
>I'm not seen the 6 mm for sale or even seen it at all!
>I have corresponded to some people on the Internet who own the 6 mm.
>
>Nikon also makes two fish eyes that are retrofocus designs,
>which means that they are "mirror down" and they work like
>any other lens. The less expensive is an 8mm F2.8, which I
>own, and the other is a 6 mm F2.8. I am not sure how many of the
>6 mm have been manufactured, but I suspect it is less than 100.
>The cost for this lens is usually listed at about $6,000. The 8
>mm is easy to find and can be purchased for $900 to 1200,
>depending on conditions.
>
>So, if you find two 6 mm F5.6 for sale, buy one for me!
>
>mk stenstrom
stenstro@stanley.seas.ucla.edu (Dr. M. K. Stenstrom 310-825-1408)