Canon 8-15mm L fisheye question

Ok I bought one awhile ago on a whim and today was the first time I used it on my 5Dmk3.I was wondering if it is for full frame or crop?? I could not zoom it without seeing the lens hood from 8-12mm...closer to 15 mm and there was no vignetting. I thought I could use it from 8-15mm without that massive amount of vignetting. It seemed to work much better on my 7Dmk2 but that makes sense because of the crop. Am I doing something wrong with the 5Dmk3?? Here is a pic at 8mm from the 5Dmk3 today.

You have to remove the lens hood when using it at the wider settings....Page 11 of the user guide

Bob

I did but it really didn't make much of a difference. It was better but not great

It's not vignetting per se, it produces a circular image at the wide end...that's how it works....page 8 of your user guide

Bob

I think it is pretty cool that the lens hood is actually (at least partially) in focus.

I am ok with the circular image...I thought the circle would have been full frame??
I will put it back on my 5Dmk3 now and see what it looks like

Thanks Bob! I got it now...I thought it was a full frame image that was circular IN NATURE...it is indeed a circle at 8mm without the lens hood

and also thats what the 10mm lock is for too. It's there for crop cameras to give a 10mm fisheye look (16mm equiv) without vignetting.

I love mine. I had one for awhile sold it and three weeks later had to rebuy another because it's that good.