5 out of 10 points and not recommended
I bought this lens as a "grab and go" for my Elan II. It was what that body was stored wearing so I could quickly deploy it in fleeting situations. (F8 and be there) Toward that end, it has a good FL zoom range, good open F, fairly fast AF and as advertised will not vignette the on board flash as long as a hood is not installed. All this at an atractive price.reviewed February 20th, 2007 (purchased for $209)
However, a few months after purchase I noticed that the image in the viewfinder would shift slightly left or right when manually reversing focus direction. I didn't think much of it given that the lens still SEEMED to give good results.
Since then I have become heavily involved in astronomy and stars are an acid test of any optical system. That combined with the recent purchase of my first DSLR has brought me to a point where I am much more critical of image quality.
I piggybacked my 30D on top of one of my scopes and shot 20- 40 second exposures of the Orion constellation through this lens. When I zoomed in on those images I found that every star in every image was stretched and or ghosted to the left to the extent that the streached dimension was double the other axis. I went back through other non-astro files as well as film blowups taken with this lens looking for images with bright objects on dark background and saw the same effect.
I veiw this lens as a good idea poorly executed and I doubt it is indicative of all examples. I take a "what do you expect for $209" attitude toward it. Had it still been under warranty I might have sent it to Canon for repair. Instead it has been sold and replaced with the 24-105 F4 L IS. Kind of expensive for IT'S Image quality but it's a lot better than the 28-105. My Orion costellation shots now have nice round star images. Well, at least in about 50% of the center of field. Hey, it's still a zoom. Compromises have to be made.