fisheye question that has bugged me.

[osirus]

Well the next lens i want to get is a nice fisheye lens.

Now theres one thing that i noticed long ago when reading up on them
and ive never understood fully..

ok.
So focal lengths with lenses.
less mm = wider fov.

now, i see fisheyes.
one says its 10.5mm
one says 8mm
one says 4.5mm

Yet they all say they give a 180 degree fov image.
so.. does that mean the 10.5mm fisheye is just as wide as the 4.5mm fisheye?

and if so.. why the different numbers?

 

[Josh66]

Well, I could be wrong - but I don't think you're going to find any lenses that can see behind you (fov>180 deg).

I think 180 degrees is the limiting factor here, and the longer fisheyes are just 'cropped' more.

 

[osirus]

well the old 6mm Nikon fisheye had a 220 degree fov so it is possible to go over 180.

 

[Josh66]

Hmm... Didn't know that, still seems kinda odd though. Wouldn't your tripod or feet show up in a picture with a 220 degree fov?

 

[osirus]

Yeah i think it would be quite hard not to get them to show up..