Announced at the beginning of September, this new Canon standard zoom lens was designed to complement the EOS 7D body on which we tested it. Providing a focal length range equivalent to 29-216mm in 35mm format, the EF-S 18-135mm f/3.5-5.6 IS covers both wide enough angles for landscape photography and is narrow enough for portraiture and sports photography. It's an excellent step-up from the standard kit lens for buyers who would like a longer zoom range.
The EF-S designation denotes a ‘short' back-focus design that can only be used on cameras with APS-C sized sensors. Vignetting (edge darkening or cut-off) will occur is the lens is fitted on a full format DSLR body.
Canon's new EF-S 18-135mm f/3.5-5.6 IS lens. (Source: Canon.)
The optical design uses 16 elements in 12 groups and environmentally friendly lead-free glass is used for all elements. According to Canon, a ‘high-precision' UD aspheric lens has been included to correct aberrations, while a six-bladed diaphragm closes to a circular aperture for attractive bokeh. Coatings on various elements have been optimised to reduce ghosting and flare.
Canon claims the built-in stabilisation system provides four f-stops of shutter speed advantage. The system automatically distinguishes between normal shooting and panning shots and selects the optimum stabilisation mode. ‘Optimised' AF control is another feature, although unlike Canon's pricier lenses, this lens relies on a gear-driven micro-motor, which is inherently slightly slower and noisier than the ultra-sonic motors on the USM lenses.
Build quality is a cut above Canon's budget kit lenses and Canon claims to have ‘improved' the exterior lens design to provide a ‘high-grade look and feel compared with previous EF-S lenses. A stainless steel mounting plate ensures a secure fit on the camera body long term and the lens feels solid. Internal focusing allows the use of angle-critical attachments like polarisers and graduated filters.
The focusing ring is a 12 mm wide band near the front of the lens barrel. It has a finely-ridged rubber coating that provides a secure grip. No support is provided for full-time manual focusing and the lens lacks a distance scale.
Behind the focusing ring is a 62mm wide zoom ring that has a 35mm thick ridged rubber collar. The trailing edge of this ring is engraved with focal length markings for 18mm, 24mm, 35mm, 50mm, 85mm and 135mm positions. On the 16mm wide section of the barrel behind these engravings are two slider switches, the top one for AF/MF and the lower for switching the stabiliser on and off.
No zoom lock is provided and none appears necessary as we noticed no tendency for zoom creep in the course of our tests. The lens is supplied with end caps but, in line with Canon's normal practice for ‘budget' lenses, no lens hood is provided. (The EW-73B lens hood has an RRP of $59.)
Handling
Being designed for the EOS 7D this lens fits the camera body very comfortably and is well balanced in the hands. Both focusing and zoom rings showed no slack yet moved smoothly and positively. The zoom ring moves through approximately 45 degrees of rotation and we found the markings on the lens barrel to be accurate for the indicated focal length settings.
The inner barrel extends approximately 42 mm as you move the zoom ring from the 18mm position to 135mm. In the process, the maximum and minimum apertures change with focal length as follows:
|
Focal length
|
Max. aperture
|
Min. aperture
|
|
18mm
|
f/3.5
|
f/22
|
|
24mm
|
f/4.0
|
f/25
|
|
35mm
|
f/4.5
|
f/29
|
|
50mm
|
f/5.0
|
f/32
|
|
85mm
|
f/5.6
|
f/36
|
|
135mm
|
f/5.6
|
f/36
|
The focusing ring moves through approximately 30 degrees in MF mode, making precise manual focusing less easy than it should be. The ring rotates a little during autofocusing but the front element remains motionless so there's no problem when angle-critical attachments are in place.
Performance
The review lens focused accurately in the AF mode with longer focal length settings, although we experienced some hunting with the longer focal length settings in low light levels. When the viewfinder was used for shot composition, AF speeds were faster than we expected from the geared AF motor and focusing was able to keep pace with the 7D's burst mode.
However, in Live View mode the contrast-based AF system on the 7D (and on other Canon cameras) was as slow as we've come to expect from Canon's Live View system. In general, noise levels during autofocusing were acceptably low - although not totally silent.
The image stabiliser enabled us to use shutter speeds as slow as 1/8 second with a focal length of 60mm, confirming Canon's claim of four f-stops stabilisation advantage. More than 90% of shots taken in our stabilisation tests were acceptably sharp at between three and four f-stops below the shutter speeds we would expect from an unstabilised lens.
Imatest showed resolution to be quite variable and revealed considerable edge softening at wide aperture settings. The 35mm focal length produced the highest overall resolution plus reasonably good edge sharpness at aperture settings of f/5.6 and smaller. But even it failed to reach the resolution levels we expected from the 7D sensor.
Edge and corner softening was quite pronounced with the 18mm focal length setting through most of its aperture range. The longer focal length settings showed reduced resolution at small aperture settings that could be due to diffraction. The graph below shows the results of our Imatest tests.
Lateral chromatic aberration was mostly in the ‘low' band, although the 18mm and 135mm focal lengths exhibited ‘moderate' CA for much of their aperture ranges. Coloured fringing could be seen near the edges of shots when they were enlarged to 100%. In the graph below, the red line marks the border between ‘negligible' and ‘low' CA with the green line separating ‘low' and ‘moderate' CA.
Barrel distortion was obvious in shots taken with the 18mm focal length but became relatively insignificant at 24mm. Slight pincushioning became visible at 50mm and moderately noticeable at 135mm. Vignetting (edge and corner darkening) could be seen in open-aperture shots at all focal length settings except 35mm. It was very obvious at both 18mm and 135mm but resolved by closing the aperture down to f/5.6 at 18mm or f/7.1 with the longer focal lengths.
Backlit subjects were handled very well, with very little loss of contrast due to veiling flare. Bokeh was also quite attractive in close-up shots - although not outstandingly beautiful.
Buy this lens if:
- You want an affordable general-purpose lens to match the 7D body.
- You'd like a lens that requires no readjustment when you fit polarisers and graduated filters.
Don't buy this lens if:
- You require high resolution at all focal lengths, along with good flatness of field.
- You need close focusing and macro capabilities.
IMATEST GRAPHS
SAMPLE IMAGES
18mm focal length, ISO 100, 1/512 second at f/8.
42mm focal length, ISO 100, 1/400 second at f/8.
135mm focal length, ISO 100, 1/400 second at f/8.
18mm focal length, ISO 100, 1/60 second at f/12.9.
100% enlargement of a section of the above image showing coloured fringing.
Vignetting at 18mm f/3.5.
Vignetting at 35mm f/4.5.
Vignetting at 135mm f/5.6.
Stabiliser test: 60mm focal length, ISO 200, 1/8 second at f/11.
Stabiliser test: 135mm focal length, ISO 200, 1/40 second at f/5.6.
135mm focal length, ISO 100, 1/40 second at f/9.9.
Additional image samples can be found with the review of the Canon EOS 7D.