CV 20mm Skopar

I have just bought a CV 20mm Skopar with the EF mount. It is manual focus if you don't know the lens.

On my 1ds MkI I cannot get a good sharp photograph at any aperture. I have scale focused, focused until the green light comes on and tried the good old fashioned method of focusing until the image looks sharp on the screen. All to no avail: I thought I had a dud.

On my D60, my 1d MkI and my 1d mkII the lens is as sharp as a tack (as they say) at every aperture from f3,5 to f16 - f22 starts getting soft but is still usable and much better than the 1ds.

The 1ds is spot on with all my other lenses 17-35, 28-70, 28, 50, 70-200 and is the sharpest of the lot - apart from my old 1dMkI which seems to cut the images out with a cheesewire.

Any ideas as to why the 1Ds is not working with the lens. Just in case you are wondering, the softness is all over.