Canon FD 15mm F2.8 fisheye on 5D!

Canon FD 15mm F2.8 known as the full-frame fisheye due to its ability to fill up the 24x36mm format has a 180° angle of view only on the diagonal of the 35mm frame's image area of 24mm x 36mm. The 15mm full-frame fisheye also focuses from 0.2 meter (8 in.) to infinity.
This lens is used on film camera but I tried to used it on Canon DSLR 5D with an FD-EOS adapter. In spite of the adapter made from Japan but it's not so good because there is a glass on it. All photo that have been taken by using FD 15mm with this adapter on Canon 5D are low on sharp and contrast. What's a pity!
This original FD 15mm lens maybe is very good on Canon AE-1!!!

Canon FD 15mm F2.8 lens connects with a Japan FD-EOS adapter (Shot by 5D + EF 85mm/1.2L mk2)

The front cap is not original and I can cover the lens by a Canon cap with 72mm diameter

Close-up photo (Canon 5D + FD-EOS adapter + FD 15mm/2.8)

Another close-up photo (Canon 5D + FD-EOS adapter + FD 15mm/2.8)

In campus of Konkuk University, Korea (Canon 5D + FD-EOS adapter + FD 15mm/2.8)

So wide with FD 15mm

This shot using a build-in filter on Canon FD 15mm (There are 4 color build-in filter on FD 15mm lens)