What you get in the box:

* G10 flange-mount to 58mm threaded adapter

* 58mm to 52mm adapter ring (and a 55mm to 52mm adapter ring you won’t need with the G10)

* Fisheye add-on lens (52mm thread mount)

* Front and rear lens caps

In other words, you don’t have to buy anything else along with this lens. If you have a Canon G10, it comes with everything you need. I had to call 47th Street Photo to confirm that.

When set up and mounted, the entire lens projects about five inches from the front surface of the camera, making it look like a miniaturized SLR.

Now that I have the lens, I understand a bit better how it works. At the camera’s widest zoom angle, the fisheye circle takes up the center 1/4 of the frame, with black around it. At about mid-zoom, the majority of the frame is image, with black corners. At full zoom, you have roughly the equivalent of the camera by itself at its widest angle, and no barrel/fisheye distortion is evident. With the variable zoom, you can choose whether you have a rectangular or circular fisheye effect, although the barrel distortion becomes much less evident as you move toward rectangular.

The glass quality is pretty good. Images are clear, and the autofocus system works correctly. Opteka recommends setting the camera to a narrow aperture and focus at infinity, although shooting in low light with normal (large aperture) settings seems to work well with the G10. There is noticeable chromatic aberration at the edges of the fisheye circle, but we’re talking about a $60 lens here.

The mount is a little shaky feeling — the add-on barrel doesn’t snick solidly into place like an SLR lens does (which is a pity, it wouldn’t have been hard to make the mount that carefully; I don’t know if this is a limitation of the camera or the Opteka mount, though). It’s not going to come off, but it’s a bit mobile on the camera, which feels a bit cheesy. The extension barrel and lens themselves are nicely machined, and appear to be high quality. Although the Opteka copy says it’s “Made and Designed in Japan” (from their website), the lens I received is clearly marked CHINA. No shock for the price, but a bit off-putting to have expectations set incorrectly (the box says “Designed in Japan” on the side, and “Made in China” on the bottom). Until I saw the CHINA marking, I would have been willing to believe the lens was made in Japan as well, so this isn’t a ding on the quality, more a ding on Opteka’s marketing department.

Due to its size, this add-on lens takes the G10 from “barely pocketable” to requiring a bag of some variety. It nearly doubles the bulk of the camera if you want to carry both G10 and fisheye with you.

I’m very satisfied with the lens, and highly recommend it if you have occasional recreational use for a fisheye lens, and don’t want to drop $700+ on a decent fisheye for your SLR. I would not recommend it for regular or professional use except as an option of last resort, mostly due to the shaky mount and likely marginal durability.

UPDATE: February 17, 2010

I have upgraded to the G11, and am pleased to report that this add-on lens also works well with the G11. There have been no problems with the lens, although it hasn’t seen a whole lot of action. I have one new gripe, which is that with the supplied lens caps, the extension tube and fisheye lens must be separated in order to have a lens cap on the back of the fisheye. It’s not a huge deal, but I’d prefer to have a rear lens cap that fits on the extension tube instead of threading onto the back of the lens unit, so I don’t have to unscrew the two pieces every time the lens is put away.
Rating: 5 / 5

In addition to the price, the battery looks cheap too. It is literally held together by just some duct tape — which I thought was part of the packaging. When I peeled it off, the inside of the battery (which is never meant to be seen…) was revealed in front of my eyes! Even though I was skeptical, it works fine when I tried it on the camera. That said, I haven’t felt comfortable enough to use it for a long time. Therefore, I cannot comment on the life span of the battery.

In hindsight, I should have splurged on the Canon replacement batteries. And for you? I’d recommend to splurge as well.
Rating: 2 / 5