Excerpt: This Sigma 4.5mm was bought for night star shots, horizon to horizon, and it does that indeed. In other uses, if one can keep one's feet out of the frame, it is wonderful for cityscapes. A walk in the park can be almost magical with this real fisheye. It is used on a crop sensor 60D, 650D, and the new 70D. Seeing the sun and my shadow both in the same frame is amazing!
Pros: Consistent Output, Easily Interchangeable, Much Fun, Strong Construction
Excerpt: So I work a lot and photography is my tool for reminding I'm a much more interesting person outside of my work. I was a paid photographer at one point, maybe I might do it professionally in future. So I was interested in this lens since I could finally get this effect on my smaller sensor camera. For instance I photographed this very old tree's roots in the foreground, the mid-ground was full of orange leaves, and the background capture the whole entire tree top.
Pros: Consistent Output, Durable, Fast / accurate auto-focus, Rugged, Strong Construction
Summary: I picked this one out for my Sony Alpha 77 from all the other options, because this one has autofocus. I take a lot of self portraits and I needed autofocus for that purpose. It is exactly what I expected, works well in low light, sufficiently sharp, and fun to use. I just think that price tag is a bit high, when you can get a manual focus one for $250.
Excerpt: This is the most extreme fish eye lens you can get for a APS-C camera. With a full 180º view, you get a full circular image, like the Sigma 8mm FE on a full frame câmera. Good lens quality. Luminous, fast and an excellent minimal distance of focus.
Pros: Clear Optics, Easy To Use, Firm Mount, Strong Construction
Summary: A nice, ultra wide angle lens. The HSM focus drive is fast and quiet. One great added feature is the adapter for the lens cap. It has 72mm threads, so unlike most ultra wide angle lenses this lens can be fitted with a protective filter, which is very important for valuable lens optics. Granted the added filter causes some vignetting, but with the circular fisheye nature of this lens the small added amount of vignetting is not really an issue.
Summary: Perhaps I got a bad lens, but this lens is far too soft for my purposes. Remember, 180 degrees of vision is squeezed into a circle within the rectangular canvas of your camera's sensor (hence circular fisheye). I intended to use this for spherical panoramas for realtime background images, but the clarity is just too low on my D5100. For that purpose, stay away from fisheyes and go wide angle so details are preserved.
Summary: This product is great except cost. If you don't mind spending around $900 then this lense is for you!!!! If you are budget minded you could get a manual lense far cheaper that produces the same great pics. The only reason for 4 stars is cost everything else is wonderful.