I'm having trouble understanding what designates a lens as a fisheye lens if the focal length is the same as (or can be the same as) a wide-angle lens.

For example - the NIKKOR 10.5mm f/2.8G ED AF DX is a Fisheye, the same with the 16mm f/2.8D. Why not just get the 10-24mm f/3.5-4.5G ED wide-angle that would cover both focal lengths and more? Is it because of the higher aperture of the fisheyes?

Hey jdeg, the difference is the zoom lens is not a true fisheye because at the 10mm setting it does not have a wide enough field of coverage (only 109 degrees). The fixed focal length lenses each cover the required 180 degrees to be considered a true fisheye lens. Even the 14mm f/2.8 is just considered an ultra-wide angle because it only covers 114 degrees not 180. Hope that helps clear it up.

Ah, I get it. Thanks Ken!

No problem, anytime.

A little more correctly.... A 10mm wide angle lens will be recti-linear (maintains straight lines as best as possible) whereas the 10.5 fisheye aarounds everything in the traditional "fisheye" sense. The 10.5 fisheye is 180-degrees **diagonally** thus it still fills the full frame rather than creating a round image that would be a full 180-degrees in all directions.

So these 10-20 / 10-24 / 12-24 etc ultra-wide angle zooms are rectilinear wide zooms, though I *think* the Tamron 11-16 (or something like it, slips my mind exactly just now) is actually supposed to be more of a true "fisheye" zoom, though of course still not the true full circular fisheye.

EricB

I have the 10.5 fisheye, and honestly, don't find it real useful. It's neat to play with from time to time, but I'd be a whole lot happier with a fast wide angle regular lens - the 14-24 2.8 is on my list for 'someday'.

I'll probably grab one of those with the D700 replacement, assuming Nikon does their usual 'instant rebate' on a camera and lens if purchased together next summer.

You can actually get Rectilinear fish-eye lenses too. The Samyang 8mm is one such

My wife and I just got a Tokina 11mm wide angle and a 10.5 fisheye. In terms of magnification they are similar, however the fisheye can take a 180 degree shot compared to about 104 on the Tokina.

If you are after an ultra wide for landscapes go for a lens like the Tokina. If you want an extreme field of view with the curvy effects get the fisheye.

I actually like both but for different things. With corrective software like DXO the fisheye pics can be corrected to give impressive panorama or even indoor shots. That said, whilst good, it is not as crisp and sharp as the Tokina.