Sony 35mm f/1.8 DT SAM ( SAL-35F18 ) - Review / Test Report - Analysis
Lens Reviews - Sony Alpha/NEX (APS-C)

Distortion

The Sony lens produces a moderate amount of barrel distortion (~1.3%). This may be noticeable but it's rarely objectionable.

Vignetting

Vignetting is a weak spot of the lens. The light fall-off reaches ~1.5EV (f-stops) at f/1.8 - this is clearly visible. The situation improves gradually but we're still facing a vignetting of ~1EV at f/2.2. The vignetting has much improved at f/2.8 and it's not relevant anymore beyond.

MTF (resolution)

The resolution of the Sony lens is generally pretty impressive. The center quality is already excellent at f/1.8 and it reaches truly outstanding results at medium aperture settings. The border quality is also very high straight from the max. aperture onwards. The corners are comparatively softer (albeit still "good") at f/1.8 and f/2.2 but they pick up quality at f/2.8 and they reach very good to excellent levels from f/4 to f/11. The global performance is absolutely superb at f/5.6 and f/8.

The contrast level is somewhat reduced at max. aperture.
The field curvature is minimal.
The centering quality of the tested sample was good albeit not perfect.

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 CAs (color shadows) are quite low with an average pixel width of around ~0.6px at the image borders.

Bokeh

The quality of the bokeh (rendering of the out-of-focus blur) is very good. Out-of-focus highlights have an smooth inner zone with only slight outlining. The highlight discs have a pretty circular shape till f/2.8 - at least in the image center. The shape deteriorates somewhat towards the corners due to vignetting effects. The aperture gets more edgy from f/4 onwards.

The important out-of-focus background (see the right-hand sample crop below) is rendered smoothly whereas the foreground (to the left) is slightly more nervous.

Bokeh Fringing

Bokeh fringing is a common problem among large aperture lenses. At f/1.8 and f/2.2 you may be able to spot purple halos in front and green halos beyond the focus point. The issue is almost gone at f/2.8 and not really visible anymore at f/4.

Move the mouse cursor over the f-stop marks below to observe the respective LoCAs
f/1.8 f/2.2 f/2.8 f/4




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