*UPDATE 30/9* added link to part 2.
This is part 1 of a 2 part review. Part 2 is here.
Why is it lens names are so long? Anyway, after shooting hundreds of photos and creating a bunch of images, I thought I'd share my observations on the Canon EF-S 17-55 f/2.8 IS (from here on in 17-55/2.8). This is not a scientific study, there are no test charts (don't even own one) but my real-world experiences. I own all the equipment, paid for from my own wallet.
Part 1: Personal observations
I'll be drawing comparisons between the 17-55/2.8 and the EF 17-40 f/4L (henceforth 17-40), which I also own. It's an abvious choice due to the focal lengths and useful fr me in that I bought the two lenses for very different reasons. The 17-40 was bought before the release of the 17-55/2.8 primarily for outdoor landscape work. I found I was increasingly using it indoors and so went for the faster aperture and IS of the 17-55/2.8. I have now been using the latter for quite a lot of landscape work from my travels.
Both lenses are well made and handle nicely. They are definitely both a step up from low to mid range zooms. That said there are differences. the 17-55/2.8 extends on zoom and has zoom and focus rings reversed. It is not weather sealed. It is also quite a bit heavier and larger.
For these reasons, I actually prefer the 17-40 as an object. the zoom and focus are a little smoother, it sits in the hand a little better (due to smaller size and weight) and it a better choice for hiking. Somehow it just has that slight edge in quality feel. Purely subjetive, nothing to do with function.
That said, the location of the IS and AF buttons are the 17-55/2.8 are nicely placed and easy to find by touch. the same cannot be said for all Canon lenses.
1b. Aberrations/distortion etc
The 17-40 has quite a lot more distortion across the range. It is clearly noticeable at wide angle, even on the cropped 20D sensor. The 17-55/2.8 has very little. When I produce stitched images i do no pre-adjustment on distortion with this lens. It also produces nicely sharp images edge to edge even wide open. From this point of view, it is highly suited to indoor architecture - one of the reasons I've got it.
1c. Image Stabiliser
A key selling point and one of the few wide angle IS lenses around (although Canon has a couple more cheaper offerings).
The claim is 3 stops but quite frankly I've never got that low. In general there's been no need or subject movement makes the point moot. I'm certainly seeing 2 stops without problem but if you're shooting people at 1/10s they aren't going to be still long enough to worry.
Indoor static sujects it certainly helps but I find I have to brace myself as body sway can affect the pictures - I don't think IS works well on such low frequency, long wavelength motion.
It does, however, enable me to continue working indoors without flash which i like. Plus some location won't allow it anyway.
1d. Image qualities
I find that the 17-55/2.8 produces very good images. Nice mid-tone contrast, carries good shadow detail. Focus is swift & accurate, even in quite poor light. No problem using AF for exposures around the 8s mark.
There are 2 things I seem to notice (and I'll be testing for part 2). First is apparant narrow plane of focus relative to aperture, the second (and, I think, related issue) is the relatively high contrast of the images coming from this lens. I could, of course be wrong.
This has intrigued me enough to go do some testing & side-by-side with the 17-40 to confirm or refute this observation.
So, for this part - I'm pretty pleased with the performance. Nice handling but not as good, IMO, as the 17-40. Good image qualities (not just sharpness). Useful IS. All the things I was looking for.
In part 2: some testing of technical aspects that piqued my curiosity.