Sony SEL 10-18mm f/4 OSS Lens Review

Sony SEL 10-18mm f/4 OSS Performance

At 10mm, sharpness in the centre of the frame is already excellent at f/4, although the clarity towards the edges of the frame is a little disappointing by comparison, just falling short of good levels. Stopping down the aperture to f/5.6 results in a great improvement in sharpness across the frame, resulting in outstanding sharpness in the centre of the frame and clarity which is just short of excellent towards the edges.

At 14mm performance at maximum aperture drops off quite severely, with clarity in the centre barely reaching good levels and clarity towards the edges of the frame being fair. Stopping down to f/8 results in much improved performance with outstanding sharpness in the centre and very good clarity towards the edges of the frame. The lens performs very similarly at 18mm also.

Resolution @ 10mm		Resolution @ 14mm
Resolution @ 18mm		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 Sony NEX-5R using Imatest.

Chromatic aberrations are reasonably well controlled, barely exceeding three quarters of a pixel width at any most apertures and focal lengths. CA's just exceed 0.75 pixel widths towards the edges of the frame at 14mm. This level may be just visible along high contrast edges towards the edges of the frame.

Chromatic aberration @ 10mm		Chromatic aberration @ 14mm
Chromatic aberration @ 18mm		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 Sony NEX-5R using Imatest.

Falloff of illumination towards the corners of the frame is quite pronounced fas you may expect for such a wide angle lens. At f/4 and 10mm the corners of the frame are 2.29 stops darker than the image centre and at 18mm this level drops to 1.86stops. Even with the lens stopped down to f/11, some darkness can still be seen in the far corners on some images, with illumination never really being visually uniform across the frame.

Distortion is very well controlled for a lens of this range with only 0.298% barrel distortion present at 10mm and 0.219% pincushion distortion present at 18mm. The distortion that is there is uniform across the frame, so should be relatively easy to correct in image editing software afterwards.

The supplied lens hood does an reasonable job of shielding the lens from extraneous light that may cause issues with flare. Even without the hood this lens is quite resistant to flare and retains good contrast, even when shooting into the light.

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