Hi guys,
Like someone on the challenge page said, you don't have to buy the adapter. Just hold it up to the body with the prime lens in reverse.
I don't know if you have tryed it, but it's not that easy
Even with the adapter the DOF is really thin and you need to put the cam on tripod to nail it decently, the distance subject-lens is VERY short and the lens blocks the light so you have to use a out camera flash, the lens should have an aperture ring otherwise you need to focus wide open and then stop down the lens manually keeping the aperture lever. Finally the CA are very high and the sharpness is only so-so.
It requires practice and patience (which I don't have

).
Here is a self-portrait from this evening: D7000, Topcon 28mm f2,8 @f16 (my best out of 50 shots and still a cr@p one! :-()
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Lol, I need an upgrade, my Nikon D6x is a too limited gear!