January 2009 | Margaret Brown
A compact, ultra-lightweight telephoto zoom kit lens for Pentax DSLR cameras.
RRP: $399.95 (when purchased separately)
Rating (out of 10):
- Build: 8.0
- Handling: 8.5
- Image quality: 8.0
- Versatility: 8.0
- OVERALL: 8.0
Most people will acquire the smc Pentax-DA L 50-200mm f/4-5.6 ED lens in the twin lens kit with one of Pentax's DSLR cameras. However, the kit lens supplied for review with the K-m camera body looked a little different from the lens shown on Pentax's website. Like the 18-55mm kit lens, the test lens lacked the green band around the rear edge of the zoom ring and focus markings in metres and feet in front of the focusing ring and no lens hood was provided.
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Most people will acquire the smc Pentax-DA L 50-200mm f/4-5.6 ED lens in the twin lens kit with one of Pentax's DSLR cameras. However, the kit lens supplied for review with the K-m camera body looked a little different from the lens shown on Pentax's website. Like the 18-55mm kit lens, the test lens lacked the green band around the rear edge of the zoom ring and focus markings in metres and feet in front of the focusing ring and no lens hood was provided.
The RRP provided with the specifications applies to the smc Pentax DA 50-200mm F4-5.6 ED lens when purchased separately. It's reasonable to expect a cylindrical lens hood to be included with this lens, although we're not sure whether it's supplied with the kit lens we reviewed.
For a 50-200mm zoom, this kit lens was surprisingly small and light, the latter being due to the extensive use of lightweight plastics in its construction. Build quality was reasonably good, although the lens mount is plastic and felt a little rough when it was attached to the camera body.
According to Pentax's specifications, it consists of 11 elements in 10 groups with an ED (Extra-low Dispersion) glass element to counteract chromatic aberration. Autofocusing relies on a slotted drive screw, which is controlled by the camera body. This means noticeable focusing noise in AF mode. Six diaphragm blades close to produce a near-circular iris. Optical surfaces appear to have been coated to reduce flare and ghosting but we have no information on the nature of these coatings.
The zoom ring is closer to the camera body. It's approximately 38 mm wide with a 25mm wide, deeply-ridged grip. The trailing edge carries engraved marking for the 50mm, 80mm, 100mm, 135mm and 200mm settings.
Just in front of the zoom ring is a 25mm wide focusing ring that steps down at the front for roughly half of its length. Fine ridges on its trailing edge provide a grip. A bayonet moulding around the front of the lens appears to be designed for the lens hood and there's a white mark for lining it up when it is fitted.
The front of the lens is threaded to accept 52mm filters. The only accessories supplied with the review lens were end caps.
Handling
This lens is a good, lightweight partner for the K-m body and easy to attach, although, as mentioned, the plastic mount grated a little as it was turned on the metal mounting plate on the camera body. Moving through the zoom range requires just under a quarter of a turn, which extends the lens by approximately 35 mm. The lens rotates during both focusing and zooming, making it unsuitable for use with angle-critical attachments.
The focusing ring moves through roughly 180 degrees as you traverse its range. Focusing movement is relatively smooth but positive and we found no tendency for the lens to 'creep' when it was carried pointing downwards. No zoom lock is provided. The focusing ring locks firmly when the camera is in AF mode and no manual fine-tuning is possible.
Performance
In bright conditions, autofocusing was generally fast and accurate and the camera locked onto subjects almost instantaneously. However, we noticed some hunting as light levels became lower. Images were slightly more contrasty than shots from the Pentax 18-55mm lens we tested but still required a little fine-tuning in an image editor to deliver bright, sharp-looking pictures.
Imatest showed the best performance to come from the 100mm focal length setting between f/5.6 and f/11. Edge softening was quite pronounced at wide apertures at all focal lengths but reduced dramatically when the lens was stopped down. Resolution declined progressively from f/11 onwards and we would not recommend using this lens with apertures smaller than f/16 or wider than f/5.6. The graph below shows the results of our tests.
Lateral chromatic aberration was in the 'low' band at all focal length settings but came close to crossing into the 'moderate' band with the 50mm focal length. The graph below shows the results of our tests.
The red line marks the border between 'insignificant' and 'low' CA, while the green line is the boundary to the 'moderate' band.
Some coloured fringing was noticeable in shots taken in contrasty outdoor lighting but we had to enlarge image files to 100% to see it. Sample images are shown below.
The full image. (Note: vignetting can also be seen in this shot.)
A crop from a 100% enlargement showing the effects of edge softening and coloured fringing.
Rectilinear distortion was barely noticeable throughout the test lens's zoom range. Typical of a tele zoom, there was slight barrelling at the 50mm end and minor pincushioning at full tele extension. Vignetting was evident at wide apertures with all focal length settings. However, it had largely vanished by between f/6.7 and f/8.
Flare was surprisingly well constrained for a lens without a lens hood and it's reasonable to expect some improvement in performance when the lens hood has been fitted. Bokeh was better than expected for a lens of this calibre.
Buy this lens if:
- It's bundled with a Pentax camera and, therefore, represents good value for money.
Don't buy this lens if:
- You use manual focusing a lot.
- You shoot in low light levels.
- You're hard on equipment. (Because of its lightweight construction, this lens won't tolerate rough handling.)
IMATEST GRAPHS
SAMPLE IMAGES
50mm focal length, 1/250 second at f/6.7.
200mm focal length, 1/250 second at f/6.7.
Close-up at 50mm; 1/90 second at f/4.
Vignetting; 50mm focal length, 1/1000 second at f/4.
Vignetting; 200mm focal length, 1/500 second at f/5.6.
Flare; 50mm focal length, 1/125 second at f/11.
200mm; 1/180 second at f/5.6.
57.5mm; 1/80 second at f/8.
105mm focal length, 1/60 second at f/4.5.
80mm focal length, 1/125 second at f/4.5.
200mm focal length, 1/350 second at f/5.6.
200mm focal length, 1/350 second at f/8.
105mm focal length, 1/150 second at f/8.
200mm focal length, 1/25 second at f/8.
87.5mm focal length, 1/125 second at f/8.
95mm focal length, 1/80 second at f/11.
Additional image samples can be found at the end of the review of the Pentax K-m DSLR camera.
Picture angle: Equivalent to 75-300mm in 35mm format
Maximum aperture: f/4.5
Minimum aperture: f/32
Lens construction: 11 elements in 10 groups
Lens mount: Pentax KAF3
Diaphragm Blades: 6
Minimum focus: 110 cm
Maximum magnification: 1:4
Filter size: 52mm
Dimensions (Diameter x L): 66.5 x 84 mm
Weight: 260 grams