On some internet sources I read about SAMYANG 8mm Fisheye that its made for APS-C sensors and the lens is not usage for full format sensors.
if this true and if so why? (samyang also offers a 14mm fisheye where it is stated usage for APS-C and fullformat sensors...)
If you need a circular fe for fullframe consider a "shaved" Nikon 10,5mm. This produces a full circle on FX. You loose resolution of course using a circular fe on FX.
I guess your aim is to have as few shots as possible? Another way would be on your 5D2 to use a 2,8/15mm Canon fisheye in a diagonally mount camera - theyÂ´re out of production and sometimes available at a "comfortable" price (the new 8-15mm zoom is rather expensive). This way you can use the 180° diagonal fov the lens provides (Nikon provides 170° diagonally) and you donÂ´t need an extra Zenith- and Nadir shot (but Nadir must get edited of course - as it must be with all lenses).
I read very different critics of the Samyang . . i tried one some time ago and definitely wasnÂ´t impressed at all because of very massive CAs and flares. But there seem to be newer versions of better quality.
In the end itÂ´s a question of what you really need: earning money with your work or doing it just for fun. In the first case you save time having a "clean" lens - in the second case i guess spending time with lots of corrections doesnÂ´t matter too much.