Pentax DA* 16-50mm f/2.8ED AL [IF] SDM Lens Reviews

Handling and Features
Performance
Verdict
Specification



This 3.1x zoom lens provides an angle of view equivalent to the popular 24-75mm range on a 35mm format camera, when mounted on a Pentax Digital SLR. It sports a fast f/2.8 maximum aperture, which is constant throughout the zoom range, silent focusing and costs around £840. Being a DA* lens, with a gold ring around the lens barrel, it is one of Pentax's premium optics. In this review we'll take a look at how it performs.

Pentax DA* 16-50mm f/2.8ED AL [IF] SDM Handling and Features

The build quality of this lens is good with a metal lens bayonet and high quality plastics used for the construction of the lens barrel. A prominent gold ring around the lens barrel signifies this is one of Pentax's premium optics,and it sports a weather and dust resistant construction as a result. The lens isn't overly heavy for an optic with a constant f/2.8 aperture, weighing around 600g and it balances well with the Pentax K-5 IIs body used for testing.

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



The manual focusing ring doesn't rotate during auto-focus and manual adjustments can be applied at any time. Manual focusing action is quite gritty and not particularly well damped on the sample used for testing. This can make applying manual focus adjustments a little tricky, especially as there is quite a bit of play in the focus ring. Auto focus is powered by a silent motor in the lens, which is quick to lock onto subjects. The minimum focus distance of 30cm is fairly close for a lens of this type and it is close enough to pose no issues when shooting in claustrophobic environments.

Pentax DA* 16-50mm f/2.8ED AL [IF] SDM Performance

At 16mm and f/2.8, sharpness in the centre of the frame is already outstanding. Unfortunately the performance of the lens towards the edges of the frame isn't quite as good at maximum aperture, only achieving fairly good levels of clarity. Stopping down improves performance across the frame, with peak sharpness being achieved between f/5.6 and f/8. Here sharpness is outstanding in the centre of the frame and very good towards the edges.

Zooming to 28mm, results in reduced sharpness levels in the centre of the frame at maximum aperture, but performance towards the edges of the frame remains similar to 16mm. Again, stopping down to f/5.6 results in the best performance across the frame, with outstanding sharpness in the centre and excellent clarity towards the edges of the frame.

Finally at 50mm. Overall sharpness takes a hit at maximum aperture, with good levels of sharpness being achieved in the centre of the frame, but performance towards the edges of the frame can only be considered fair. Stopping down to f/8 results in outstanding sharpness across the frame at this focal length.

MTF@16mm

MTF@28mm

MTF@50mm

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 brought under better control, the more the lens is zoomed in. Fringing is most prominent at 16mm and f/2.8, where it exceeds 1.25 pixel widths towards the edges of the frame. This level of fringing may become apparent in harsh crops from the edges of the frame, or in large prints along high contrast edges.

CA@16mm

CA@28mm

CA@50mm

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 fairly typical for a lens of this range and maximum aperture. At 16mm the corners of the frame are 1.62 stops darker than the image centre and at 50mm the corners are 1.1 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 noticeable at 16mm. Easing as the lens is zoomed in. Imatest detected 4.11% barrel distortion at 16mm, which is replaced by 0.373% pincushion distortion at 50mm. 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 paramount.

During testing, this lens proved itself quite resistant to flare and contrast levels are retained well, 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* 16-50mm f/2.8ED AL [IF] SDM Sample Photos

Value For Money

Being priced at around £840, this lens is quite reasonably priced for a manufacturer's own standard zoom with a constant f/2.8 aperture. In fact, this lens is currently £10 cheaper than the recently released Pentax 20-40mm f/2.8-4 Limited lens, which has a narrower zoom range and a variable maximum aperture.

Sigma also offer a 17-50mm f/2.8 lens, which costs around £310 in Pentax fit, or Tamron also offer a 17-50mm f/2.8 lens, for around £260. Either lens may be a viable alternative for those on a budget.

Pentax DA* 16-50mm f/2.8ED AL [IF] SDM Verdict

This lens has a lot going for it, including the silent focusing, weather and dust resistant construction and the constant f/2.8 maximum aperture. It performs really well when stopped down too. Unfortunately, the sharpness delivered at maximum aperture towards the edges of the frame falls short of what you may expect from a premium lens from a camera manufacturer. If, however, you only tend to place your subject in the centre of the frame, this may not affect your photography, unfortunately, for many, this isn't the case.

Pentax DA* 16-50mm f/2.8ED AL [IF] SDM Pros

Very good sharpness when stopped down
Weather and dust resistant construction
Good build quality
Silent focusing
Full time manual focus override
Constant f/2.8 aperture

Pentax DA* 16-50mm f/2.8ED AL [IF] SDM Cons

Performance towards edges of the frame at maximum aperture
High CA levels at 16mm
Gritty and poorly damped manual focusing ring

FEATURES
HANDLING
PERFORMANCE
VALUE FOR MONEY
VERDICT

Pentax DA* 16-50mm f/2.8ED AL [IF] SDM Specifications

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