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Pentax DA* 50-135mm f/2.8 ED [IF] SDM Lens Review

Gary Wolstenholme reviews the Pentax DA* 50-135mm f/2.8 ED [IF] SDM, a bright f/2.8 constant aperture telephoto-zoom lens.

|  Pentax DA* 50-135mm f/2.8ED [IF] SDM in Interchangeable Lenses
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Handling and Features

Pentax 50 135mm DA Star Lens (6)

This 2.7x telephoto zoom lens provides an angle of view roughly equivalent to the popular 75-200mm range on a 35mm format camera. It sports a fast f/2.8 maximum aperture throughout the zoom range, silent focusing and costs around £850. Being a DA* lens, it is one of Pentax's premium optics, as signified by the gold ring around the lens barrel. In this review we'll see how it performs.

Pentax DA* 50-135mm f/2.8ED [IF] SDM Handling and Features

Pentax 50 135mm DA Star Lens (3)

The build quality of this lens is excellent, with high quality plastics used for the construction of much the lens barrel and the bayonet being constructed from metal. It sports a weather and dust resistant construction and isn't overly heavy for an optic with a constant f/2.8 aperture, weighing around 765g. As a result, it balances well with the Pentax K-5 IIs body used for testing.

The lens barrel doesn't extend, as focusing and zoom are performed internally and the filter thread does not rotate. This makes it perfect for use with polarising and graduated filters. A deep petal-shaped hood is supplied with the lens that attaches to the front of the lens via a bayonet fitting.

Pentax 50 135mm DA Star Lens (1)

The manual focusing ring doesn't rotate during auto-focus and manual adjustments can be applied at any time. Manual focusing action is not as smooth as you may expect from a lens of this level and price, on the sample used for testing. Even so, there is enough damping to make applying manual focus adjustments easy. Auto focus is powered by a silent motor in the lens, which is quick to lock onto subjects. The minimum focus distance of one metre is fairly standard for a lens of this type.

Pentax 50 135mm DA Star Lens (2)

Pentax DA* 50-135mm f/2.8ED [IF] SDM Performance

At 50mm and maximum aperture, sharpness approaches excellent levels in the centre of the frame, and falls just short of good levels towards the edges of the frame. Stopping down improves performance across the frame with peak levels of clarity being achieved between f/5.6 and f/8. Here sharpness is outstanding in the centre and excellent towards the edges of the frame.

Zooming to 70mm results in similar performance at maximum aperture, with very good sharpness being produced in the centre of the frame and fairly good clarity towards the edges. Peak performance is realised at f/8 at this focal length. Here sharpness is outstanding across the frame.

Finally at 135mm, sharpness falls just short of very good levels at maximum aperture and clarity towards the edges of the frame is fair. Stopping down just one stop to f/4 results in outstanding performance in the centre of the frame, but it takes until f/8 until sharpness reaches very good levels towards the edges of the frame.


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 for the most part; remaining well under one pixel width at all settings bar 50mm and f/22. As a result, fringing should rarely be an issue, even in harsh crops from the edges of the frame, or in large prints with high contrast edges.


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 well controlled for a lens of this range and maximum aperture. At 50mm the corners of the frame are 0.8 stops darker than the image centre and at 135mm the corners are 1.2 stops darker. Visually uniform illumination is achieved with the lens stopped down to f/5.6 or beyond throughout the zoom range.

Distortion is fairly mild at either end of the zoom range. Imatest detected 0.7% barrel distortion at 50mm, which is replaced by 1.68% pincushion distortion at 135mm. The distortion pattern is uniform across the frame, which should make it relatively easy to apply corrections in image editing software afterwards if straight lines are necessary.

During testing, this lens proved itself resistant to flare and contrast levels are good, even when shooting into the light. The petal-shaped hood does a decent job of shading the lens from extraneous light that may cause issues.

Pentax DA* 50-135mm f/2.8ED [IF] SDM Sample Photos

Value For Money

Being priced at around £850, this lens is priced quite reasonably for a manufacturer's own tele-zoom with a constant f/2.8 aperture, especially as there aren't currently any direct equivalents available for Pentax cameras.

Pentax DA* 50-135mm f/2.8ED [IF] SDM Verdict

This lens has been around a while now, but it still manages to hold its own well against the very latest lenses available from other manufacturers. It delivers very good sharpness in the centre of the frame at maximum aperture, and excellent sharpness across the frame when stopped down. The price of around £850 isn't too much to ask for a quality manufacturer’s own-brand lens either, especially given the excellent build and weather sealing.

  The Pentax DA* 50-135mm f/2.8ED delivers very good sharpness with a constant f/2.8 aperture.

Pentax DA* 50-135mm f/2.8ED [IF] SDM Pros

Excellent sharpness across the frame, when stopped down
Very good sharpness in the centre at maximum aperture
Weather and dust resistant construction
Good build quality
Silent focusing
Full time manual focus override
Constant f/2.8 aperture

Pentax DA* 50-135mm f/2.8ED [IF] SDM Cons

Performance towards edges of the frame at maximum aperture
Slightly gritty manual focus action on sample used for testing


Pentax DA* 50-135mm f/2.8ED [IF] SDM Specifications

Lens Mounts
  • Pentax K SMC-DA
  • Pentax KAF
Focal Length50mm - 135mm
Angle of View11.9 - 31.5
Max Aperturef/2.8
Min Aperturef/22
Filter Size67mm
35mm equivalent75mm - 202.5mm
Internal focusingYes
Maximum magnificationNo Data
Min Focus100cm
Box Contents
Box ContentsFront cap, Rear cap, Lenshood, Soft case

View Full Product Details


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18 Jun 2014 1:09PM
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