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White Balance

The S90 offers only the most basic of control over white balance - aside from the default auto setting there are only four presets (tungsten, fluorescent, cloudy and daylight). There is no 'manual' or custom white balance - hardly surprising in a camera of this class (though hardly unheard of). Although the S90 struggled under tungsten lighting when shooting our test chart it did a better job with fluorescents. In real world use we found auto white balance to be consistently reliable when shooting outdoors and under fluorescent lighting. Under tungsten (incandescent) lighting the results broadly reflect what our test chart shows - all exhibit a warm (or at times downright orange) color cast, which disappears altogether if you switch to the tungsten white balance preset.

Outdoor - Auto WB
Red -0.1%, Blue 0.6%

Fluorescent - Auto WB
Red 3.4%, Blue -7.1%
Incandescent - Auto WB
Red 12.7%, Blue -19.3%

Flash Performance

Flash hasn't traditionally been Sony's strong point, and the unit on the S90 is usable, rather than outstanding. On the positive side, the color is almost perfect and the output is throttled down well when shooting nearby subjects, meaning blown-out results are rare. The red-eye reduction mode is as effective as a pre-flash can be, but the delay it adds between pressing the shutter and the picture being taken is unacceptable.

Skin tone
Slight warm tone, good exposure
Color chart
Excellent color, very slight under exposure

Macro Focus

The S90 has a dedicated macro mode that works at all focal lengths, but - as is normal in cameras such as this - is most effective towards the wide end of the zoom. It's not the most impressive macro mode we've ever seen, with a minimum focus distance of around 10cm giving you an area of just over 9cm across to work with, but focus is very reliable. Inevitably there is some distortion at the wide end of the zoom, and a little corner softness, though it's not as strong as some of the S90's competitors (mainly I suspect due to the fact it doesn't focus as closely).

Wide macro - 93 x 70 coverage
25 px/mm (625 px/in)
Distortion: Average
Corner softness: Average
Equiv. focal length: 39 mm
Tele macro - 147 x 110 coverage
16 px/mm (397 px/in)
Distortion: Average
Corner softness: Low
Equiv. focal length: 117 mm

Barrel and Pincushion Distortion

Whilst there is measurable distortion at the wide end of the zoom (around 1.2%), it is no worse than most ultra-compact 3x zooms. It certainly doesn't have a significant impact on real-world shots. Edge sharpness leaves a little to be desired (and you can see the fringing effect of chromatic aberration in this shot), though it does improve as focus distance increases. There is barely noticeable (0.5%) pincushion distortion at the long (117mm equiv.) end of the zoom range.

Barrel distortion - 1.2% at Wide angle
Equiv. focal length: 39 mm
Barrel distortion - 0.5% at Telephoto
Equiv. focal length: 117 mm

Noise Comparison

Here for visual comparison are three identical shots taken at 80, 100, 200 and 400 ISO settings in our studio. Sony's noise reduction is fairly harsh, but it does produce very smooth-looking results even at ISO 400 (helped by the inherently less noisy nature of the 4MP chip compared to some of the higher resolution alternatives). There's no doubt that ISO 80 to 200 are perfectly usable, and that the ISO 400 setting is fine as long as you're not intending to print too large.

ISO 80 100% crop ISO 100 100% crop
ISO 200 100% crop ISO 400 100% crop

Specific Image Quality Issues

Very little to complain about here, certainly as far as the target market is concerned. Color is excellent; vibrant without being artificial, focus accuracy - even in low light - is excellent, and the noise levels are very low. Exposure is almost 100% reliable (only giving minor problems in scenes with extremely high contrast, and even then rarely), and dynamic range seems good even given the fairly high default contrast. The images are not going to impress purists - they're a little 'over processed', but for the 'point-and-shoot' crowd producing prints at 5.7 inches or less they look great. There is a slight softness to the images, but this is better than the usual over-sharpening, and the image does look a lot crisper when you add a little unsharp masking in post-processing. And, like the Canon PowerShot A520, the big selling point is the consistency of results in a wide variety of shooting situations - this is another camera that rarely wobbles, no matter what you throw at it. We found very little color fringing and no evidence of vignetting.

Color fringing

Not a major issue at all, we did find some purple fringing in areas - such as this - of high contrast and slight overexposure. Compared to other entry level cameras it's not serious problem, and only affects a tiny proportion of exposures (and only at the wide end of the zoom).

100% crop 39 mm equiv., F2.8
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