Pentax SMC DA 18-270mm f/3.5-6.3 SDM Lens Review

Handling and features
Performance
Verdict
Specification


This lightweight 15x zoom lens from Pentax offers one of the largest zoom ranges currently available, focusing powered by a supersonic drive motor and costs around £550.

Pentax SMC DA 18-270mm f/3.5-6.3 SDM Handling and features

All things considered, this lens is incredibly lightweight for the range it covers, weighing only 453g. As a result is balances perfectly on the Pentax K-5 IIs used for testing, even without a battery grip. High quality plastics have been used throughout the construction of the lens barrel and the lens mount is metal. Unlike many recent Pentax lenses, this lens is not sealed against dust and moisture.

Focusing is performed internally, so the 62mm filter thread does not rotate, making it perfect for use with polarising and graduated filters. The wide rubberised zoom ring is smooth to operate, not tightening up considerably at any point in the range, but having enough resistance to avoid zoom creep. A thinner manual focusing ring rotates during auto-focus, so care may need to be taken to prevent it accidentally catching your fingers during operation. Even so, it doesn't move all that quickly. Manual focusing action is smooth, but not damped at all, which can make applying fine focus adjustments slightly fiddly. This lens isn't equipped with the Pentax 'Quick Shift' feature either, which means autofocus needs to be completely disengaged to apply manual adjustments. The focusing ring is locked in place, engaged with the focus motor in AF mode.

Although focusing is powered by a supersonic motor, it isn't overly quick, especially at 270mm, where it can hunt for focus for what seems like quite a while. The minimum focus distance of 49cm is fairly close for a lens covering this range.

Pentax SMC DA 18-270mm f/3.5-6.3 SDM Performance

Sharpness starts off extremely high, reaching excellent levels at f/3.5 and 18mm. The clarity towards the edge of the frame lags behind somewhat at maximum aperture for this focal length, only reaching fairly good levels. Stopping down improves sharpness across the frame and peak sharpness is achieved at f/8 for this focal length. Here sharpness is outstanding across the frame.

As is typical for high zoom ratio lenses, performance drops off as the lens is zoomed towards its telephoto setting. At 70mm sharpness reaches good levels in the centre of the frame at maximum aperture, but falls short of fair levels of clarity towards the edges. Peak quality across the frame is achieved at f/11 for this focal length. Here sharpness is excellent across the frame.

Finally, at 270mm, sharpness can only be considered as fair in the centre of the frame, and fairly poor towards the edges of the frame. Stopping down to f/11 results in a great improvement in performance with sharpness in the centre reaching very good levels, and fairly good levels towards the edges of the frame.

Resolution @ 18mm		Resolution @ 70mm
Resolution @ 270mm		How to read our charts The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column. The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple. For this review, the lens was tested on a Pentax K-5 IIs using Imatest.

Chromatic aberrations are well controlled at shorter focal length settings, but zoom the lens to 270mm and fringing becomes very strong indeed towards the edges of the frame, exceeding two pixel widths. This level of fringing may pose issues with high contrast edges placed near the extremities of the frame.

Chromatic aberration @ 18mm		Chromatic aberration @ 70mm
Chromatic aberration @ 270mm		How to read our charts Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software. Apochromatic lenses have special lens elements aspheric, extra-low dispersion etc. to minimize the problem, hence they usually cost more. For this review, the lens was tested on a Pentax K-5 IIs using Imatest.

Falloff of illumination is reasonably well controlled for a lens with an 15x zoom range. At 18mm and f/3.5 the corners of the frame are 1.53 stops darker than the image centre and visually uniform illumination is achieved with the lens stopped down to f/5.6 or beyond. At 270mm the corners are only 1.26 stops darker than the image centre and visually uniform illumination is achieved at f/11.

Distortion is often a weak point with high zoom ratio lenses, and although there is 4.9% of barrel distortion at 18mm and 1.61% pincushion distortion at 270mm, these values are quite low for this kind of lens. The distortion pattern remains uniform across the frame at either end of the zoom range, which should mean applying corrections in image editing software after will be fairly straightforward.

During testing, this lens proved itself quite resistant to flare and contrast levels remain good, even when shooting into the light at most focal lengths. A petal shaped lens hood is supplied with the lens, which does a decent job of shielding the lens from extraneous light that may cause issues.

Pentax smc DA 18-270mm f/3.5-6.3 ED SDM Sample Photos

Value for money

Being available for around £550, this lens seems quite expensive, especially when compared to its closest equivalent. The Pentax 18-250mm f/3.5-6.3 lens is very similar, just losing 20mm of telephoto range and can be picked up for around £420.

Sigma's 18-250mm f/3.5-6.3 DC Macro HSM lens is another alternative that may be considered by Pentax camera owners. This lens is 20mm shorter at the telephoto end, but it focuses closer and is available for around £405.

Pentax SMC DA 18-270mm f/3.5-6.3 SDM Verdict

Lenses that cover high zoom ranges such as this lens are always a bit of a compromise. However, this lens does perform well at shorter focal lengths, but the lack of sharpness at the telephoto end my be enough to put many prospective purchasers off this lens. Even so, when used within its limitations it is still more than capable of producing decent results. If the convenience of having one lens that covers all situations is the most important consideration, then this could be the lens for you.

Pentax SMC DA 18-270mm f/3.5-6.3 SDM Pros

15x zoom range
Good build quality
Excellent performance at shorter focal lengths
Light weight

Pentax SMC DA 18-270mm f/3.5-6.3 SDM Cons

Sharpness is compromised at 270mm and maximum aperture
CA levels are high at 270mm
No manual focus override or 'Quick Shift' focusing

FEATURES
HANDLING
PERFORMANCE
VALUE FOR MONEY
OVERALL

Pentax smc DA 18-270mm f/3.5-6.3 ED SDM Specifications

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