The Canon EF-S 18-135 mm f/3.5-5.6 IS lens is considered to be an economical choice but with clutched image stabilization and an amazing 7.5x zoom range which is equal to 29-216 on a 35 mm camera is everybody’s pick. The image stabilizer assures sharp shots at shutter speed up to four stops slower than without stabilization. The look of the lens is pretty eye catchy with barrel of the lens made out of texture finished plastic and silver ring besides focus control. The zoom ring can be managed easily because of the broad rubberized grip. Focus execution takes place internally because of which front filter does not rotate while zooming thus making polarizing filters easy.
The image stabilizer also supports automatic panning and tripod detection. It gives a modest act as far as optical zoom is concerned. The lens gives it highest performance at f/5.6 with superb centre resolution and decent at the edges of the frame. It still gives centre down to f/16.
This lens uses an AF micro-motor (DC) besides usual Canon USM. However, there is no FTM (full time manual focusing) but auto focus speed is reasonable. The lens has 6 circular aperture blades and a filter size of 67 mm. The chromatic aberration (CA) is well controlled if maintained less than 18mm.It usually offers a CA pixel width of 1.2-1.5px at the borders. With 1.31% pincushion distortion you get negligible barrel distortion: it might be noticeable in significant applications as can be seen in the following picture.
The distortion is quite standard towards the edges so it is not difficult to do the necessary changes to the image through image editing software later.
Although the low price of this lens and dimensions, the Canon EF-S 18-135mm IS seems to be very robust and stable. To take care of the lens, I suggest you to buy a UV filter, so your lens can be easily protected from shocks.
Distortion is a problem, as some tests show, especially at 18 mm and 135 mm. The lens has an evident barrel distortion from 18 to 22 and this aspect could limit the use in this range. To be honest I thought the lens could be worse, but I find that the lens is in the average.
The Canon EF-S 18-135 mm f/3.5-5.6 IS lens is vulnerable to strong light source and tends to produce flare and loose contrast: if intense light hits the front element of the lens it causes mass of brightly colored ghosts to emerge in the image. A lens hood can avoid this affect, you will have to spend some more money for the same, but in general it costs few pounds. This Canon EF-S lens is DxOMark certified which ensures independent and RAW based image quality performance data and makes sure that you choose the right equipment. One can always check on the test and results of DxOMark certified product on-line on their website.
Nevertheless, the lens is lightweight and it has good quality resolution at optimum apertures and image stabilizer that is effective there are few setbacks. The issue with flare can be easily resolved if company choose to offer hood with the lens complementary because it is easy to get lens at discounted rate when bought with camera kit. Also few issues which might affect the performance of the lens are the chromatic aberrations and barrel distortion which occurs at 18mm, this kind of problems frequently affects low cost lenses or lenses with an high focal excursion.
Although the lens quality is not perfect, the Canon EF-S 18-135 mm f/3.5-5.6 IS lens is one of the best solution for who can not spend a lot of money and for who would like to use only a single lens without change it every time.