) with the Canon Digital Rebel XT. Both are very similar and unfortunately share similar flaws.The lens is compact and lightweight and, aside from being included as a part of various Canon kits, also sells separately for around $100. Now, $100 is considered cheap for a dSLR lens and not much is expected for this amount. And as such, this lens delivers, but no more.
For comparison purposes (albeit comparing apples to oranges to some extent), I got my Nikon 28-80mm f/3.3-5.6 G Wide Angle-Telephoto Autofocus Zoom Lens with the Nikon N55 camera. That lens used to sell for about $80 and aside from shoddy plastic-fantastic construction was way better in many respects. So I know that good performance is possible for $100 and even less, and on this count the Canon lens in question does not deliver.
Focusing
The lens has a switch to toggle between manual and automatic focusing. The lens has a motorized outer focus ring, which you can also use to focus manually when the camera switch is set to MF.
If you select MF position for manual focus, you can rotate the ring around the lens until the subject you want to focus on is in focus. I want to point out that the lens has no distance markings on the focus ring and thus I cannot use the depth of field tables to figure out where I need to focus to get the depth of field I need at the given focal length.
When used on cameras with Depth of Field (DOF) preview, this is less of an issue, but is still not ideal because this slows down the DOF estimation. And the focus ring itself feels very slightly flimsy. But for the price, I have nothing to complain about in this respect.
In manual focus mode, the focusing ring has the tendency to rotate if you are using a polarizer and have to adjust it by rotating it. In this case, you have to hold the focus ring with one finger while rotating the polarizer ring with other two. In auto focus mode, this is not as big of an issue since after the focusing is done, the ring is stopped, but the problem is you can't set the polarizer first, then focus; you have to pre-focus, set the polarizer, then focus again.
One of the reasons I bought a camera with this lens was the fact that I wanted a wide-angle-capable lens (ideally about 28mm focal distance in 35-mm equivalent). This 18-55mm lens with 1.6x crop factor zooms from 29 to 88mm, which is what I need. The zooming is by the wide well-textured ring, which feels well damped and has no zoom creep.
Aperture Control
This lens has no aperture ring and the aperture is set using camera controls. I would like to have an aperture ring, but that would probably raise the price of the lens. The shape of the aperture has effect on Bokeh ("Blur" in Japanese - for improved control of out-of-focus highlights). Unlike the aforementioned Nikon lens, this lens doesn't seem to have nice Bokeh; it is pretty generic.
The maximum aperture of the lens in f/3.5 at 18mm wide-angle and f/5.6 at telephoto.
Performance
I mostly like modes where I myself can choose either aperture (to control depth of field) or the shutter speed (to control blur caused by handheld camera operation or the moving subjects). Most of the time I use the former.
For the price, the lens works well. The pictures are mostly sharp, with good detail level, contrast and colors. The sharpness is very good in the center of the frame with slight blurring in corners overall. The best results (sharpness) are achieved when the lens is used in the middle of its zoom range and when it is stopped down several stops from wide open: about f/5.6-8 closer to wide angle and f/8-11 closer to telephoto.
Shots at f/8 and smaller apertures were very good. The portraits shot at f/8-11 apertures came out with the sharp subject and perfectly blurred background.
The geometric distortions (barrel at wide angle and pincussion at telephoto) are as expected at this price range. The chromatic aberration (purple fringing) in the areas of high contrast are pretty significant, but not unexpected.
As I said above, the performance for the price is ok, although Nikon lens mentioned before manages to do much better for less. The problems with this Canon lens are as follows.
To get decent sharpness, you have to stop it down to f/5.6-11, and even then the corners of the frame are not very sharp. This means you have to use the camera with a steady subject, on a tripod and/or at higher ISO settings, none of which is versatile. And higher ISO settings lead to blurriness of its own kind and noise.
So if you need to shoot in low light and/or need to get very shallow or very deep depth of field while retaining sharpness, this lens isn't for you. For my purposes, it doesn't work well anymore since I need to take pictures of my son while he is playing in his Excersaucer indoors and he won't sit still with a plastic fish in his mouth while I use f/11 at ISO below 800. So I need a lens that would produce sharper photos at wider apertures.
Reliability
I have used various variants of this lens for a few years with no issues.
Pros: Low price, decent performance.
Cons: Low sharpness wide open, not best for low light.
Bottom Line
For the price, this lens produces good results but not much more. If you need to shoot in low light, a better result can be obtained by getting a lens with better sharpness at wider apertures, including Canon's own image-stabilized 18-55 IS lens.
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