Samsung 20-50mm f/3.5-5.6 ED NX i-Function Zoom Lens

Samsung 20-50mm f/3.5-5.6 ED NX i-Function Zoom Lens Performance

Sharpness at 20mm and maximum aperture is good in the centre of the image, but only fair towards the edges of the frame. Stopping down improves performance, with sharpness in the centre reaching excellent levels in the centre at f/5.6 and across the frame at f/8.

Zooming to 35mm results in an overall increase in sharpness at maximum aperture, with sharpness in the centre being very good and fairly good towards the edges. Just like at 20mm stopping down to f/8 results in excellent sharpness across the frame.

Performance in the centre of the image area falls off a little at 50mm, but the clarity towards the edges improves to good levels at maximum aperture. Stopping down to f/8 provides very good sharpness across the frame.

Resolution @ 20mm		Resolution @ 35mm
Resolution @ 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 Samsung NX200 using Imatest.

Chromatic aberrations are well controlled, only exceeding half a pixel width towards the edges of the frame at 50mm. These low levels of fringing should pose few issues, even in large prints.

Chromatic aberration @ 20mm		Chromatic aberration @ 35mm
Chromatic aberration @ 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 Samsung NX200 using Imatest.

Falloff of illumination towards the corners is reasonably well controlled. At 20mm the corners are one stop darker than the centre at maximum aperture and visually uniform illumination is achieved at f/5.6. At 50mm falloff is reduced to half a stop, with visually uniform images being produced at f/8.

Distortion is very well controlled throughout the zoom range. Only 0.123% barrel distortion is present at 20mm and only 0.38% pincushion distortion at 50mm. These low distortion levels shouldn't pose many isssues for general photos and should be easy enough to correct in image editing software afterwards as the pattern is uniform across the frame.

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