Sony 11-18mm f/4.5-5.6 DT ( SAL-1118 ) - Review / Test Report - Analysis
Lens Reviews - Sony Alpha/NEX (APS-C)
Tuesday, 11 March 2008 13:24

Distortion

Typical for many ultra-wide zoom lenses the Sony produces pronounced barrel distortion at 11mm (2.7%) which ease continuously towards the long end of the zoom range (0.9%).

Move the mouse cursor over the focal length text marks below to observe the respective distortion
11mm 14mm 18mm

The chart above has a real-world size of about 120x80cm.

Vignetting

Typical for most dedicated APS-C lenses the Sony 11-18mm DT produces some vignetting at wide-open aperture but the issue is actually well controlled for an ultra-wide lens - the maximum vignetting remains below 1EV and when stopping down by 1 f-stop the problem isn't really significant anymore (for this type of lens).

MTF (resolution)

The Sony 11-18mm f/4.5-5.6 DT produced rather a mediocre resolution characteristic in the MTF lab. The center performance is generally stellar throughout the whole range but at 11mm and 14mm there's a sharp drop at the borders and more so in the extreme corners . This is rather critical for an ultra-wide lens where the complete foreground needs to be sharp in large depth-of-field situations. The quality improves somewhat towards the 18mm setting but all-in-all the performance is rather disappointing. The lens (a different sample) has already been tested on the Alpha 100 last year but the results were pretty much in line with the current findings. You're welcome to check out the provided sample images below which reflect the results.

In case you wonder about the strange MTF curve - usually the lens quality peaks around f/5.6 before diffraction starts to take its toll (in the center at least) and the Sony 11-18mm f/4.5-5.6 is simply a slow speed lens.

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) are quite extreme both at 11mm and 18mm peaking way beyond 2px on the average at the image borders. The problem is easily visible and disturbing in field images unless you correct the issue via an imaging tool.




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