A fast, lightweight and affordably-priced short-telephoto prime lens for Pentax K-mount cameras.

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The SMC Pentax-DA 50mm f/1.8 lens was developed as a fast, lightweight short-telephoto prime lens for the company’s K-mount cameras. Covering a focal length equivalent to 76.5mm in 35mm format, it is sharp, fast and relatively inexpensive. However, it lacks weatherproof sealing and its AF system isn’t as sophisticated as Pentax’s more expensive lenses. We tested this lens with the new K-3 DSLR.

The optical design of this lens is simple, with six elements in five groups. No exotic lenses are listed in the specifications. SP (Super Protect) coating on the front element repels dust, water and grease and makes it easier to keep the lens clean. The SMC tag indicates the presence of multilayer SMC coatings to suppress internal reflections and minimise ghosting and flare.

Who’s it for?
 The focal length of this lens makes it ideal for portraiture and its fast f/1.8 maximum aperture gives photographers plenty of scope for depth of field control. Rounded diaphragm blades enable it to produce natural-looking blurring of out-of-focus areas.

Extensive use of plastic in the construction of the lens makes it compact and light enough to carry almost anywhere. These features also make this lens well suited to street photography, particularly in low light levels.

In summary
The SMC Pentax-DA 50mm f/1.8 is a solid performer that compares very favourably with similar lenses from other manufacturers. It’s a pity it has a plastic lens mount and noisy autofocusing; but that’s almost inevitable for a compact and lightweight lens with a low price tag.

Even though we found sharpness across the frame at wide apertures a little low, the acutance and resolution in the centre of the frame at mid-range aperture settings was impressive. Couple that with negligible distortion, minimal chromatic aberration and extremely low levels of vignetting and you have a lens that provides excellent value for money.  

The focal length of this lens makes it ideal for portraiture and its fast f/1.8 maximum aperture gives photographers plenty of scope for depth of field control. Rounded diaphragm blades enable it to produce natural-looking blurring of out-of-focus areas.

The use of plastic in the construction of the lens makes it compact and light enough to carry almost anywhere. These features also make this lens well suited to street photography, particularly in low light levels.

See full review with specs, test charts and sample images

Rating

Build

8.5

Handling

8.5

Autofocusing

8.3

Image quality

8.8

Versatility

8.5

OVERALL

8.8

RRP:  AU$200; MSRP US$280 (discounted to US$199)