In summary
‘All-in-one’ zoom lenses are popular with photographers who want a single, do-everything lens on a capable camera body. Travellers, family photographers and snapshooters will find its medium-wide to medium-tele range useful for subjects as diverse as portrait, landscapes and family events.
Fitted to one of the Pentax weatherproof DSLR bodies (such as the K-S2 we used for our tests), this lens will suit a wide range of outdoor photographers and is rugged enough to be carried on bushwalks or treks. Internal focusing keeps the front element from rotating during focusing, enabling hassle-free use of angle-critical filters, such as polarisers.
Autofocusing is driven by a Direct Current (DC) micromotor, which is reasonably fast and quiet. The built-in Pentax Quick Shift system allows manual focus over-ride in single-shot AF mode by simply turning the focusing ring.
Full review
Introduced in September 2010, the smc DA 18-135mm f/3.5-5.6 ED AL [IF] DC WR lens has become one of the kit lenses offered with Pentax DSLR cameras. Covering focal lengths equivalent to 27.5-207mm in 35mm format, its 7.5x zoom range suits a wide range of shooting conditions. A simplified weather-resistant construction with six layers of sealing within the lens enables it to withstand damp conditions (including mist and light rain or spray).
Side view of the smc DA 18-135mm f/3.5-5.6 ED AL [IF] DC WR lens with the lens hood in place. (Source: Ricoh Imaging.)
The optical design is fairly complex, involving 13 elements in 11 groups and including two aspherical lens elements and one ED element. Proprietary Super Protect (SP) coating repels dust, moisture and grease, making the lens easier to clean. The lens accepts 62 mm diameter filters and comes with a petal-shaped plastic lens hood plus front and end caps. (No lens hood was supplied with the review sample.)
Who’s it For?
‘All-in-one’ zoom lenses are popular with photographers who want a single, do-everything lens on a capable camera body. Travellers, family photographers and snapshooters will find its medium-wide to medium-tele range useful for subjects as diverse as portrait, landscapes and family events.
Fitted to one of the Pentax weatherproof DSLR bodies (such as the K-S2 we used for our tests), it will suit a wide range of outdoor photographers and is rugged enough to be carried on bushwalks or treks. Internal focusing keeps the front element from rotating during focusing, enabling hassle-free use of angle-critical filters, such as polarisers.
Autofocusing is driven by a Direct Current (DC) micromotor, which is reasonably fast and quiet. The built-in Pentax Quick Shift system allows manual focus over-ride in single-shot AF mode by simply turning the focusing ring.
Build and Ergonomics
Comparatively small and light for its zoom range, the DA 18-135mm lens is very well built for its price, with a nice balance between metal and high-quality plastic components. It has a solid metal mounting plate and the zoom mechanism extends two inner barrels which are quite tightly contained. We found no evidence of play when the inner barrels were fully extended and no zoom creeping occurred when the lens was carried pointing downwards.
This lens has only two control surfaces: a 45 mm wide zoom ring just behind the bayonet mounting for the lens hood and a much thinner (10 mm wide) manual focusing ring. Both rings have textured rubber cladding, the focusing ring being the rougher of the two.
The trailing edge of the zoom ring carries indicator marks for the 18mm, 24mm, 35mm, 50mm, 70mm, 100mm and 135mm focal lengths, which are aligned with a linear marking on the fixed section of the lens barrel, which sits just below the pentaprism housing when the lens is on a camera. Each step in the zoom range changes the maximum and minimum apertures, as shown in the table below.
|
Focal Length |
18mm |
24mm |
35mm |
50mm |
70mm |
100mm |
135mm |
|
Maximum aperture |
f/3.5 |
f/4 |
f/4.5 |
f/4.5 |
f/4.5 |
f/5.6 |
f/5.6 |
|
Minimum aperture |
f/22 |
f/29 |
f/32 |
f/32 |
f/32 |
f/40 |
f/40 |
Extending the zoom to the 135mm position makes the lens roughly 50 mm longer. Interestingly, there appears to be some communication between the lens zoom mechanism and the K-S2 camera body we used for our tests. When the camera’s HDMI port is tightly closed, zooming feels rather stiff.
Open the cover to the HDMI port just a little and the zoom moves freely. At the same time, you can feel air escaping from the HDMI port. We can’t explain why this occurs but it seems to happen with several Pentax DSLRs as a couple of other reviewers have commented on it.
Manual focusing isn’t as easy as it might be, partly because of the narrow focusing ring and partly because of its position. The soft stops that indicate the limits of the focus are also easily overlooked so you often go past the end points without realising.
The closest focusing distance is 40 cm, where the lens provides a magnification of 0.24x (approximately 1:4) at the 135mm focal length.
Performance
Our Imatest results from the supplied lens were disappointing since it failed to meet expectations for the 20-megapixel sensor on the Pentax K-S2 camera we used for our tests. Subjective assessment of test shots showed most were acceptably sharp. although never truly pin-sharp.
Applying unsharp masking in Photoshop post-capture made a visible improvement, particularly in the centre of the frame where the resolution is highest. But unless you stop the lens down to between f/7.1 and f/10, the edges and corners of the frame appear a little soft. This was confirmed in our Imatest tests, and shown in the graph of the results below.
Lateral chromatic aberration was within the ‘low’ band for all focal length and aperture settings. In the graph below, the red line separates negligible and low CA, while the green line marks the border between low and moderate CA.
We found some evidence of coloured fringing in shots taken with the lens on the review camera, although only in raw files because the K-S2 provides automatic correction for chromatic aberration in JPEG files. In-camera corrections are also provided for vignetting and rectilinear distortions, both of which were noticeable in raw files from the camera.
Slight vignetting was found at the maximum aperture settings with all the focal lengths we tested. The corner darkening was heavier with the 18mm focal length, where it was equivalents to roughly one f-stop. It’s less obvious at the other focal lengths and barely visible when you stop down by about one f-stop.
Rectilinear distortion is typical of this type of zoom lens. Barrel distortion is obvious at 18mm but swaps to slight pincushioning at around 25mm, reaching maximum pincushion distortion somewhere between 25mm and 50mm and then becoming a mixture of pincushion distortion at the edges and slight barrel distortion in the centre of the frame.
Flare was reasonably well-controlled and our tests would probably have produced better results if the bundled lens hood had been provided with the lens. We found both veiling flare and flare artefacts in shots taken with the sun just outside the frame.
The visibility of flare varied with lens focal length and how far the light source was from the edge of the frame. Normal backlighting presented no problems with longer focal lengths but some artefacts were evident with the 18mm focal length when the sun was outside the frame.
Autofocusing was generally fast and accurate, even in low light levels. The AF motor was also reasonably quiet and barely audible on movie soundtracks.
Bokeh was reasonably smooth, particularly with longer focal lengths and when the camera was set to the Macro scene pre-set (which focuses closer and uses 1/3EV or 2/3EV down from the maximum lens aperture). We found no evidence of outlining around brighter de-focused areas.
Conclusion
Although the lens we tested wasn’t particularly sharp, it’s important to remember it’s a sample of one and may not reflect all lenses in the production run. However, several other reviews we’ve checked have also reported on its lack of edge and corner sharpness.
Whether that matters is up to each individual photographer. It’s probably less important to portrait, sports and wildlife shooters than landscape or architectural photographers. The former will find corner softening largely irrelevant as their shots concentrate on subjects in the centre of the frame; the latter will expect edge-to-edge sharpness.
For everyday photographers, this lens will deliver ‘good enough’ performance with an affordable price tag. Most will appreciate the wide angle-of-view coverage and find it convenient to have a weather-resistant lens to pair with one of the Pentax weatherproof cameras.
For its type, this lens is also relatively small and light, which are sought-after characteristics for travellers. So while we can’t give it an Editor’s Choice nomination, there are still some good reasons to consider it if it does the main things you want.
SPECS
Picture angle: 76 degrees to 11.9 degrees
Minimum aperture: f/22-f/40
Lens construction: 13 elements in 11 groups (including two aspherical lens elements and one ED element)
Lens mounts: Pentax K-AF
Diaphragm Blades: 7 (circular aperture)
Focus drive: DC micromotor
Stabilisation: N.a. (Pentax DSLRs have in-body stabilisation)
Minimum focus: 40 cm
Maximum magnification: 0.24x
Filter size: 62 mm
Dimensions (Diameter x L): 73.0 x 76.0 mm
Weight: 405 grams (429 grams with hood)
Standard Accessories: Front and end caps plus PH-RBC 62mm lens hood
TESTS
Based on JPEG files captured with the Pentax K-S2 camera.
SAMPLES
Vignetting at 18mm f/3.5.
Vignetting at 35mm f/4.5.
Vignetting at 80mm f/5.6.
Vignetting at 135mm f/5.6.
Rectilinear distortion at 18mm.
Rectilinear distortion at 35mm.
Rectilinear distortion at 70mm.
Rectilinear distortion at 135mm.
18mm focal length, ISO 100, 1/200 second at f/7.1.
35mm focal length, ISO 100, 1/160 second at f/7.1.
70mm focal length, ISO 200, 1/200 second at f/7.1.
135mm focal length, ISO 200, 1/200 second at f/7.1.
18mm focal length, ISO 100, 1/200 second at f/9.
Crop from the above image enlarged to 100% to show edge softening and coloured fringing.
Close-up at 18mm focal length, ISO 100, 1/30 second at f/4.5.
Close-up at 135mm focal length, ISO 100, 1/20 second at f/5.6.
523: Close-up with the camera in Macro mode; 135mm focal length, ISO 200, 1/40 second at f/6.3.
35mm focal length, ISO 100, 1/160 second at f/7.1.
Crop from the above image enlarged to 100% showing image softening in the centre of the frame.
Crop from the same image enlarged to 100% after unsharp masking in Photoshop.
Strong backlighting at 18mm focal length showing flare artefacts, ISO 100, 1/640 second at f/4.
Strong backlighting at 80mm focal length showing veiling flare, ISO 100, 1/800 second at f/4.
Normal backlighting; 18mm focal length, ISO 100, 1/640 second at f/8.
Normal backlighting; 35mm focal length, ISO 100, 1/320 second at f/9.
Normal backlighting; 80mm focal length, ISO 100, 1/200 second at f/5.6.
Normal backlighting; 135mm focal length, ISO 100, 1/160 second at f/5.6.
135mm focal length, ISO 800, 1/30 second at f/7.1.
Additional image samples can be found with our review of the Pentax K-S2 camera.
Rating
RRP: AU$549; US$479.95
- Build: 8.9
- Handling: 8.5
- Image quality: 8.0
- Versatility: 8.8