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.
|Sharpness||A spectacular performance at wideangle settings, where the lens is impressively sharp across most of the frame at both the 16mm and 24mm settings, although with rather soft corners wide open. However sharpness falls off towards the telephoto end, especially at wider apertures, where we see quite precipitous falls in the graphs towards the corners of the frame.|
|Chromatic Aberration||As usual, chromatic aberration is most obvious at wideangle, with strong red/cyan fringing visible at 16-24mm. At intermediate focal lengths CA is generally well controlled, before creeping back at the telephoto end; there's a little red/cyan fringing at 70mm, and it becomes clearly visible again at 105mm. The fringe widths also tend to increase noticeably on stopping down.|
|Falloff||We consider falloff to be a potential problem when the corner illumination is a stop or more lower than the centre. As is common for wideangle zooms, falloff is visible at the widest settings, with a maximum of 1.7 stops wide open at 16mm; stopping down to F6.3 or smaller will essentially eliminate the issue. At 24mm and beyond falloff is not an issue. Not a bad performance at all.|
|Distortion||Distortion is (as always) most pronounced at wideangle, with 1.7% barrel at 16mm. This is also a complex 'wave' type distortion, with re-correction towards the corners, which makes software correction relatively difficult. The rest of the range shows pincushion distortion, with a maximum of 1.7% at 35mm; which might be just about on the verge of visually disturbing for some scenes. Overall a pretty good showing here.|
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.
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|
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.
|F8, Alpha 700||F5.6, Alpha 700|
|100% crop, camera JPEG||100% crop, camera JPEG|
|100% crop, RAW, ACR with CA correction||100% crop, RAW, ACR with CA correction|
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|