It's found under several different brand names. Even changes focal lengths in some of them (because of allowances in focal length labeling).
This newer version adds a chip for synching to the Nikon digital APS-C DSLRs. It is manual focus only, but the chip lets you use the camera's focus confirmation, and allows the aperture to be controlled thru the camera, so it even works in Program mode.
The lens feels solid, has some heft to it, and mounts perfectly to the camera bayonet mount. Earlier versions had some reviews saying the fit was a bit tight, but that seems to be fixed.
The focus ring is just stiff enough to allow you to set a distance and forget it if you want. It doesn't budge during normal use, but it will move if you grab the lens by it. I set it at a hyperfocal distance for what aperture I'm using, often about 1m, and this gets me depth of field from rather close out to infinity even at f/5.6
I shot into the sun, into sodium vapor lights, and with flash, and saw little or no lens flare or ghosting. The images are sharp and have neutral color rendition.
Over all, I approve of this lens. Useful for realty work like raw files for virtual tours or just as wide interior shots, landscapes, any time you need an ultra wide coverage, and for creating special perspective effects.
Some unretouched sample pics:
