Sony 50mm f/1.8 DT ( SAL-50F18 ) on Sony NEX - Lab Test / Review - Analysis
Lens Reviews - Sony Alpha/NEX (APS-C)
Article Index
Introduction
Analysis

Distortion

The Sony lens produces a slight amount of barrel distortion (~0.9%). This is usually not relevant in field conditions.

The results have been taken from the corresponding A700 review. The distortion characteristic does not change between the different test scopes here.

Vignetting

The 50mm f/1.8 covers the APS-C image circle only so it produces a comparatively high amount of vignetting. At f/1.8 it exceeds 1.1EV which will be visible in some scenes. However, stopping down to f/2.2 resolves most of the issue and it's not really relevant anymore from f/2.8 onwards.

The vignetting analysis is based on directly obtained JPEGs. The Sony NEX-5 has obviously a different contrast graduation than the A700 resulting in slightly different results.

MTF (resolution)

The Sony lens was capable of delivering a pretty high resolution throughout the tested aperture range. The center performance is already excellent straight at f/1.8 and the contrast level is also very snappy here already. The borders/corners are good from f/1.8 to f/2.8. The edge to edge quality increases the more you stop down and it reaches its very good peak around f/5.6. The field curvature is marginal.

Sony NEX has a higher MP image sensor as well as an AA filter with a different characteristic compared to the A700. We're also using a different RAW converter for the NEX tests.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Lateral chromatic aberrations (color shadows at harsh contrast transitions) basically non-existent. This adds to the high sharpness perception of the lens.

Verdict

Optically speaking, the Sony 50mm f/1.8 DT ( SAL-50F18 ) is a good performer on the Sony NEX. The lens is sharp even at f/1.8 and it reaches more than very good results across the image frame around f/5.6. Lateral CAs are absolutely negligible which adds to the high sharpness perception. The lens produces some slight amount of barrel distortion but it's not really field-relevant. Typical for a dedicated APS-C format lens it shows rather significant vignetting at f/1.8. The quality of the bokeh is generally very good although out-of-focus highlights suffer somewhat from vignetting effects at large apertures. The bokeh fringing is pronounced at large aperture and the issues dissolves only gradually when stopping down.

The Sony 50mm f/1.8 DT is a budget lens and it's most obvious in its build quality - it is a plastic lens down to the mount. That's nothing bad per se but the quality doesn't feel overly reassuring. The AF performance via the LA-EA1 adapter is a quite a let down. Sony promised a functional AF on the Sony NEX but the focus performance is basically non-existent here. The lens hunts up and down its focus range with rare success. Manual focusing is usually faster and actually also more reliable. As unfortunate as it may be you should consider this to be a manual focusing combination only.

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