K 8.4/2.8 Fish-Eye
For a long time it was thought that this lens existed only as a prototype, but in early 2004 one lens was offered for auction at Yahoo Japan. The lens appears to be essentially identical to the prototype “smc PENTAX BIRDS-EYE 1:2.8 8.4 mm”, but it carries the name “smc PENTAX FISH-EYE 1:2.8 8.4 mm”. The lens shown for auction did not have the rubber ring between the aperture ring and the mount (visible on the prototype lens), but I think that it was because it had fallen off and not due to a production redesign.
Something very interesting about this lens is that it lacks a focusing ring! But at this short focal length, the depth of field is so huge, so no wonder…
The optical diagram and size information comes from this paper. Apparently the lens was designe by Satoru for Asahi Optical and is sepecified in Japanese patent JP60-153018.
|Exact Name||smc PENTAX FISH-EYE 1:2.8 8.4 mm|
|Year of Introduction||Photokina 1982|
|Sold with Hood||—|
|Sold with Case||unknown|
|Optical Formula||10 elements in 7 groups|
|Aperture Range||f/2.8 ~ f/11|
|Number of Aperture Blades||unknown|
|Minimum Focusing Distance||lens has no focusing ring|
|Maximum Magnification||depends on the lens-to-subject distance|
|Special Features||fish-eye lens|
|Maximum Diameter||81.6 mm|
|Special Features||manual diaphragm|