- Compact and lightweight
- EF-S Mount lens
- Optical image stabilization and dynamic IS
- 29-216mm focal length range equivalent to 35mm
- Stepping motor and inner focusing system
- 16-element (in 12 groups) optical design with one GMo aspherical and one UD lens elements
- 67mm filters
- Manual focus override
- 7-blade circular diaphragm
- Supports Movie Servo AF feature
- Zoom ring lock lever
Canon 18-135 IS STM is a standard to short telephoto telezoom lens with an EF-S mount. The previous version of this lens 18-135 IS was first announced in 2009 along with Rebel T4i/ EOS 650D. The company came up with a new version of the lens, the 18-135 IS STM, on June 8, 2012. The lens was introduced as an alternative kit lens for 650D and is now also an alternative kit lens for the Rebel T5i/EOS 700D. The lens is equipped with a new autofocus technology, STM (stepping motor) that was designed to achieve smooth and silent continuous autofocus while shooting video.
Design and Performance
The lens is a bit heavier than its predecessor and weighs around 480g and is 96mm in length. The lens is mainly made from black polycarbonate and has a metal mount which surrounds the extending plastic element.
The casing of the lens starts with a fixed ring that has different markings such as EFS 18-135mm, IMAGE STABILIZER and the information regarding the minimum focusing distance which is 0.39m. There are two switches on the right side of the ring to control stabilization (STABILIZER ON/OFF) and focusing mechanism mode (AF/MF). There is also a white switch next to them that makes the alignment with the camera easier. A LOCK switch beside these blocks the focal length scale at 18mm.
The 42mm wide zoom ring has 30mm ridged rubber armor. The edge of the ring is marked with focal length positions: 18mm, 24mm, 35mm, 50mm, 85mm, and 135mm. The zoom ring rotates 54 degrees as you move through the focal length range. There is also a 13mm manual focus ring that is approx 10mm behind the edge of the outer barrel. The ridged rubber coating provides a secure grip. Unlike its predecessor, this lens has a manual focus override in the AF mode. However, it lacks the distance scale. Both the rings move quite smoothly.
The optical design of the 18-135mm IS STM comprises 16 elements in 12 groups in which one of them is GMo aspherical and one is made of UD (Ultra Low Dispersion) glass. There is a 7-blade circular aperture that can be closed down to a particular value ranging from f/22 to f/36.
Autofocus: The lens boasts an STM mechanism that makes the focusing quick and noiseless. The stepping motor autofocus system lets the lens deliver a quiet and smooth autofocus operation (particularly) while shooting video. The lens took less than a second to focus from infinity to close-focus. The lens does not offer a full-time manual focus operation. But you can adjust the focus manually by halfway pressing the shutter button (autofocus can be overridden manually) without switching to the manual focus mode. The 67mm filters do not rotate.
Image Resolution: We must say that the performance is decent for a zoom lens with a wide range. Upon our tests, we found that the MTFs exceed 40lpmm at almost every focal length at the maximum relative aperture. There were no focal length lags. You cannot ask for excellent resolution when it comes to a lens of these types. Though the MTF never exceeded 50lpmm at any focal length, Nikkor could exceed a bit above 50lpmm but only at the shortest focal length.
Chromatic Aberration: When it comes to the lateral chromatic and special aberrations, some issues became apparent with this lens. We could easily spot the CA at focal lengths ranging from 18-35mm. The level is nearly 0.12% at almost any aperture which is quite decent if we compare it with its predecessor (0.15% at 70mm). However, the CA is unnoticeable when we stopped at 70mm but peeped in again at the maximum focal length. Coming to the special aberrations, we did not notice any focus shift effect.
Vignetting: The vignetting level is quite high at the 18mm and f/3.5 combination. Though the performance of Nikkor AF-S DX 18-140mm f/3.5-5.6G ED VR is much better, the performance of Canon 18-135 IS STM has slightly improved as compared to its predecessor. The vignetting drops by f/4.0 which decreases further at f/5.6 and almost diminishes by f/8 and f/11 apertures.
At 35mm and 70mm focal length and at the maximum relative aperture, the vignetting reaches to a certain extent which decreases by f/5.6 and level gets decreased further by f/8. The effect once again increases at 135mm which diminishes at f/11.
Distortion: The entry-level megazoom lenses usually have issues with the distortion correction and this lens is no exception. You get some amount of barrel distortion (-4.20%) at the widest angle. We also noticed some traces of moustache distortion (-4.93%) as well.
But fortunately, these deformations can only be seen at a wide angle. The performance quickly improved when we tried to increase the focal length. The barrel distortion diminishes to -1.08% at 24mm which turns into the pincushion distortion of +0.70% at 35mm. we could see some color fringing near the edge of the shots when they were cropped to 100%.
Bokeh: The backlit subjects were well-handled with a little loss of contrast. Coming to the appearance of out-of-focus areas, we must say that the bokeh performance is surprisingly good. However, we noticed a lighter rim and truncations in the corners that appears due to vignetting. But again we should not forget that we are dealing with a standard megazoom lens.
Should You Buy the Canon EF-S 18-135mm f/3.5-5.6 IS STM Lens?
Canon EF-S 18-135mm f/3.5-5.6 IS STM Lens is priced at $292. The lens is compact and lightweight and is sensibly designed to please the users. It offers an IS system that provides up to four-stop shake correction throughout the entire zoom range.
The lens offers quick and quiet autofocus system and supports Movie Servo AF feature. The dynamic IS is appearing for the first time that uses a wide IS correction range to let the users shoot steady videos while walking.