Here you can see the front of the 18mm, including the metal hood, which secured by use of a bayonet, ensuring it could never come loose.
While this lens is a design from the earliest days of Minolta lenses, is extraordinarily slow and needs to be manually stopped down, I mention it because while not marked as a fisheye lens it is actually Minolta’s first fisheye, and is normally considerably less expensive than the later MC and MD fisheye lenses. With a 180 degree diagonal angle of view and 124 degrees horizontal coverage, it is a fixed focus design of 7 elements in 5 groups. Accessories included a yellow and UV filter that screw into the rear of the lens, plus a custom metal cap which is secured with a bayonet mount, and a scalloped lens hood which mounts in the same manner. One of the two filters must be installed at all times, as they actually form part of the optical formula of the lens.
The lens is a good performer for it’s low price, as evidenced by this shot, taken at F/9.5. Sharpness, while not spectacular, remains easily good enough for enlargements to 8 x 10, and probably larger.

The lens provides a great introduction to the fisheye format to a minolta user on a budget, and at around US$150 on ebay it is less than half the normal price of any of the later full frame fisheye lenses. The slow maximum aperture of f/9.5 can require a tripod for lower light shots, but surprisingly it is easy to use despite the dark viewfinder, as being focus free, all that is required is to point and shoot.

Performance of the lens is acceptable, and certainly a lot sharper than any of the screw in fisheye adapters available for someone seeking to experiment with the format. That said, it is certainly softer than the later designs, possibly due to the fact that it relies upon the hyperfocal distance for sharp focus, rather than being able to be focused manually. Accordingly, for maximum sharpness I recommend that the lens be stopped down to f/16 or f/22 if possible. Coatings were significantly less advanced than the later MC and MD designs, an important issue if shooting in a location where direct light falling on the front element of the lens is very bright.

This view of the rear of the lens shows the screw in UV filter, which formed part of the optical formula for the lens. Make sure that the lens has at least the UV filter before buying. A yellow filter was also provided for use in black and white photography.
I used my 18mm f/9.5 extensively until reaching the conclusion that I used it so often that I was justified spending the money upgrading to a faster 16mm f/2.8 design. I subsequently sold this lens to help fund the purchase of the 16mm.

In summary, despite its age and obvious shortcomings when compared to the later MC and MD full frame fisheye lenses, it is a solid performer, and for a small price it gives the photographer a capacity to experiment with the striking effect of a fisheye lens.