White Balance

Just like other recent PowerShot digital cameras the S400's automatic white balance setting worked better in natural light, under incandescent light there was a visible orange cast. The preset white balance settings are excellent and provide accurate white balance which is almost indistinguishable from manual white balance.

Outdoors, Auto	Outdoors, Cloudy (or Sunny)	Outdoors, Manual
Incandescent, Auto	Incandescent, Incandescent	Incandescent, Manual
Fluorescent, Auto	Fluorescent, Fluorescent (or H)	Fluorescent, Manual

Macro Focus

Like a lot of compact cameras the S400's macro ability is to be found at the wide angle setting. The disadvantages of this are barrel distortion and shadows cast by the lens (short subject to lens distances). Best possible horizontal frame coverage was approximately 53 mm (2.1 in).

Flash Performance

The S400's flash unit has a specified range of 3.5 m (11.5 ft) at wide angle and 2.0 m (6.6 ft) at telephoto. In our tests flash exposures were fairly consistently underexposed. The S400 does not have flash exposure compensation so there would be no way to increase flash power in these situations.

Skin tone - Natural color, no blue cast, under- exposed.	Color patches - Good color balance, no color cast, moderately underexposed.

Night exposures

The S400 has an automatic noise reduction mode which is enabled for exposures of 1.3 seconds or slower. To achieve such long exposures you must first enable the camera's "long exposure" feature. Select a long exposure from the FUNC menu, press 'SET' with the exposure compensation setting visible and it will switch to long exposure. The S400 supports long exposures of 1 to 15 seconds. Noise reduction works by taking a 'dark frame' after the main exposure and using any noise from that frame to remove noise in the main shot. As expected the S400 took good night exposures with no visible 'hot pixel' noise.

Long exposure: ISO 50, 4 sec, F2.8

Barrel and Pincushion Distortion

The S400's three times optical zoom lens provides a zoom range of 36 to 108 mm (equiv). At full wide angle it exhibited 0.9% barrel distortion, at telephoto pincushion distortion was not visible. A very good performance.

Barrel Distortion, 0.9% @ wide angle	Pincushion Distortion, none @ telephoto

Vignetting / Light fall off

Our vignetting / light fall off test is very simple, a shot of a blank wall from two meters away, vignetting will always be most visible at wide angle and maximum aperture and will start to disappear at smaller apertures and/or further zoom. As you can see below the S400 exhibits very little corner vignetting / light fall of, there is just the hint of it most visible in the top right and bottom corners, it's unlikely you would see this in a normal shot.

Slight corner vignetting visible at wide angle and maximum aperture (F2.8)	No noticeable vignetting at telephoto

Purple Fringing (Chromatic Aberrations)

The S400 exhibited some chromatic aberrations around contrast detail against bright backgrounds such as in the example below. It's less than we have seen from other cameras and is a consequence of the compact design of the lens system.

Some fringing visible in the corners of shots with high contrast	Our standard chromatic aberration test shot

Overall Image Quality / Specific Issues

The PowerShot S400 produces very nice images, low noise, good color, good tonal balance and yet still detailed. The S400 is a good example of the progressive improvement Canon are able to apply to their cameras, each generation slightly better than the last. At first S400 images can appear to be a little soft, but this is simply a function of Canon's conservative approach to image sharpening, look closely however and you'll see that images still maintain very high detail levels. Colors are accurate and strong, with good delivery of foliage green and skin tones. I had no specific issues with the S400's image quality. Kudos Canon.