Studio Tests

NOTE the line marked 'Nyquist Frequency' indicates the maximum theoretical resolution of the camera body used for testing. Whenever the measured numbers exceed this value, this simply indicates that the lens out-resolves the sensor at this point - the calculated MTF values themselves become meaningless.

This lens has an optical design which can only be described as ambitious, and not for the first time we see distinctly mixed results from our studio tests. Sharpness is very good at wideangle but less impressive at telephoto, where results are particularly soft wide open. Chromatic aberration is also an issue at the wide and telephoto ends of the zoom range.

Macro Focus

A distinctly average performance here, with much lower magnification that the 18-70mm kit lens (as is typical for an internal focus design). Maximum magnification is 0.11x, achieved at a minimum focus distance of about 39.5cm, and a working distance of 21.5 cm from the subject to the front of the lens.  Image quality is very good in the centre even at F5.6, and the corners sharpen up progressively on stopping down. There's a fair bit of blue/yellow CA visible on our test chart image, but this is unlikely to have a huge effect on real-life shots.

Macro - 206x137 mm coverage Distortion: Mild pincushion Corner softness: Medium Focal length: 105 mm (157.5mm equiv)

Specific image quality issues

As always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests.

Corner softness

This lens has a distinct propensity to display soft corners wide open, as revealed by our studio tests, so the question is whether this is a practical issue in real-life shooting. It's worth highlighting the visual difference between the effects at wideangle, where sharpness falls abruptly in the extreme corners, and in the mid-range of the zoom, where there's a more gradual drop off in performance across the frame from centre to corner.

The 100% crop below is taken from the lower left of the image (not quite the extreme corner) at 16mm F3.5, and shows a marked drop in resolution even across a 240 x 180 pixel sample, with individual blades of grass reasonably defined in the top right, but reduced to mush in the lower left. In fairness it must be said that this only affects a small proportion of the frame (and where there's unlikely to be any key image content); it can also be addressed by simply stopping down to F8 or so, which you're likely to be doing with a wideangle anyway. However if you have a pathological dislike of soft corners wide open, this isn't the lens for you.

16mm F3.5, Alpha 700	100% crop

This sample at 35mm and F5.6 illustrates the more gradual drop in resolution across the frame seen in the middle of the zoom range at wider apertures. Here even the top edge of the frame is slightly soft compared to the centre, and the extreme corner distinctly blurred. Again things sharpen up on stopping down to F8-F11, so it's not too difficult to work around, but we'd generally expect to see sharper results than this from a premium lens.

35mm, F5.6, Alpha 700	100% crop, centre

100% crop, top centre	100% crop, top left

Chromatic Aberration

We expect to see chromatic aberration at the wideangle end of a lens of this type, but what is less common is the intense red/cyan fringing this lens also displays at telephoto. Fortunately, due to the near-linear shape of the CA curves (as measured in our studio tests), the fringing is easy to eliminate if you are prepared to shoot RAW and process using a converter with CA correction capabilities; for example using our standard, Adobe Camera Raw, a setting of + 40 red in the lens correction tab worked well.

16mm F8, Alpha 700	105mm, F5.6, Alpha 700

16mm F8, 100% crop, camera JPEG	105mm F5.6, 100% crop, camera JPEG

100% crop, RAW, ACR with CA correction	100% crop, RAW, ACR with CA correction

Flare

One area where the Sony 16-105mm excels is in its handling of flare. Even with the sun placed in the corner of the frame at 16mm, it gives little in the way of flare patterns, which is unusual for a design with so many elements. It deals well with strong side- or back-light too, with minimal loss in contrast even when the sun is directly impinging on the front element but out of frame.

16mm F8, sun in corner of frame	70mm F9, strong backlight

Background blur ('bokeh')

One genuinely desirable, but difficult to measure aspect of a lens's performance is the ability to deliver smoothly blurred out-of-focus regions when trying to isolate a subject from the background, generally when using a long focal length and large aperture. Sony make a selling point of this lens's circular aperture, which is supposed to ensure smooth background blur.

In practice the lens can certainly produce some pleasant transitions between areas of the image which are in and out of focus, but bokeh is not particularly smooth, with sharply delineated edges to specular highlights. It's not at all bad, but not that special either.

105mm F5.6, Alpha 700	100% crop

105mm F5.6, Alpha 700	100% crop