Pentax SMC DA* 55mm f/1.4 SDM

Gary Wolstenholme takes a close look at this short telephoto lens from Pentax.

This 55mm f/1.4 lens from Pentax is designed to be used with their latest generations of DSLR cameras and sports a bright maximum aperture of f/1.4 and silent SDM focusing for around £600, which I feel is a little pricey for a lens around the 50mm focal length.

Sigma offer a Pentax-compatible 50mm f/1.4 lens, which retails for around £380 and also includes a silent focusing motor, which clearly shows how pricey this Pentax optic is.

Pentax SMC DA* 55mm f/1.4 SDM: Handling and features
Being a DA* lens, it offers many of the features found amongst Pentax's top line of lenses, including weather sealing and a generally higher level of build quality. The lens does feel very solid and is slightly longer than many standard lenses from other manufacturers, probably due to the extra 5mm of focal length. As it is a 55mm lens, and not a straight fifty, on Pentax DSLRs it offers an equivalent angle of view of an 82.5mm lens on a 35mm camera. This focal length is considered ideal for portraiture, being almost equivalent to the classic 85mm focal length.

The SDM silent focusing system results in fast focusing speeds, although not as fast as other Pentax SDM lenses I've tested, such as the 200mm f/2.8. The SDM focus motor requires a pretty recent Pentax DSLR for full compatibility. Owners of the K100D, *istD, *istDS and *ist DL will have to muddle through with manual focus when using this lens.

In use the lens handles well thanks to the excellent build and full time manual focus override. The light weight means this optic will balance well on even the most compact Pentax SLRs.

Pentax SMC DA* 55mm f/1.4 SDM: Performance
This optic certainly proved itself capable of excellent results during testing. At f/1.4 the lens may not be as sharp as some might desire, but for portraiture this may be just what the doctor ordered. Stopping the lens down just one stop to f/2 results in superb sharpness in the centre of the frame.

Peak quality across the frame is achieved at f/5.6 where the resolution is superb across the frame. The sharpness holds up well across the frame at smaller apertures too, still producing images with good resolution across the frame at f/22.

Resolution at 55mm

How to read our graphs 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-7 using Imatest.

As is the case with simple lens designs such as this, chromatic aberrations are rarely an issue. The levels detected by Imatest are low enough to cause few issues, even with very large print sizes.

Chromatic Aberrations at 55mm

How to read out 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-7 using Imatest.

Falloff of illumination towards the corners is pretty well controlled for a wide aperture lens. At f/1.4 the corners are 1.76 stops darker than the image centre and stopping down to f/2.8 leads to visually uniform illumination.

As you may expect with a fixed focal lens, distortion is also well controlled. Imatest could only detect 0.801% barrel distortion, which should pose very few problems in normal use. If this amount of distortion is an issue, you'll be glad to know that the distortion pattern is uniform across the frame, which should make corrections in image editing software quite straightforward.

Click on the thumbnail for a high resolution image.

Superb sharpness is possible across the frame when the lens is stopped down.

Flare and ghosting is well controlled, only appearing in images taken under extreme conditions, such as lights shining straight into the lens when shooting at maximum aperture. A deep circular hood is provided, which does an excellent job of keeping unwanted light off the front element, further reducing the chance of flare ruining images.

Pentax SMC DA* 55mm f/1.4 SDM: Verdict
This 55mm lens from Pentax is without a doubt a superb performer. Unfortunately, despite the excellent sharpness to images when stopped down, and great build quality, this kind of performance isn't uncommon for a standard lens. For me £600 just seems a little too much, especially when the cost of equivalent lenses from other manufacturers is taken into consideration.

Pentax SMC DA* 55mm f/1.4 SDM: Pros
Excellent optical quality from f/2 onwards
Fast focusing
Weather selling
Low distortion and CA

Pentax SMC DA* 55mm f/1.4 SDM: Cons
Limited compatibility with older Pentax DSLRs
Price
A little soft at f/1.4

FEATURES
HANDLING
PERFORMANCE
VALUE FOR MONEY
OVERALL

Pentax SMC DA* 55mm f/1.4 SDM: Specification

Price	£600.00
Contact	www.pentax.co.uk
Filter size	55mm
Format	APS-C
Construction	9 elements in 8 groups
Angle-of-view	28.6 degrees
35mm equivalent focal length (on APS-C body)	82.5mm
Internal focusing	No
Image stabilisation	No
Minimum focus	45cm
Maximum aperture	f/1.4
Minimum aperture	f/22
Weight	375g
Size	66 x 70.5mm
In the box	Lens hood, Soft Case

The Pentax SMC DA* 55mm f/1.4 SDM costs around £600 and is available from Warehouse Express here:

Pentax SMC DA* 55mm f/1.4 SDM

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