Canon 15 2.8 Fisheye - a "minimum" fisheye ?

Some shots I take with the 15 2.8 are very curved and others have almost no fisheye effect according to the position you hold it.

Strange lens that it's sometimes fisheye and sometimes not.
What's the purpose then, isn't it better to have a 100% extreme fisheye (like the 8-16) or just a UWA ?

From what mm's can we speak of fisheye actually on Fullframe ?

It's always going to distort the images, but if what you're shooting is already coming towards you, then the appearance of the distortion will also seem less. Also, if you have no straight lines in the image, it's harder to tell.

Anyhow, it's not the lens, it's what you're shooting.

I've seen landscape shots with a fisheye that had absolutely no fisheye look to them at all and I actually find them the most appealing of all. Very natural looking