Image Quality

Sony Alpha A57 review – Image Quality

For the most part the A57’s metering system is sound, although it appears easily led into underexposure. Those capturing JPEGs may be inclined to leave on the DRO feature, as in such circumstances it helps to lift shadows to a more balanced exposure – otherwise, exposure compensation may be easily dialed in when required. In more balanced conditions there’s little to fault.

There’s also little reason to venture into the white balance presets, as most of the time the auto white balance system gets things right. In natural lighting the system is perfectly capable of assessing and reproducing most scenes accurately, and in conjunction with an appropriate Creative Style option can deliver images with brilliant colour straight out of the camera. The real test for any auto white balance system is under artificial light, and it’s here where things can come undone. Sometimes the auto system is surprisingly accurate (even under mixtures of artificial light), although on other ocassions (particularly under incandescent sources) it’s way off the more faithful reproductions achieved with the relevant preset.

The Standard Creative Style proves itself to being perfectly appropriate for many scenes, while the other options, if used correctly, also all find their use. The only instances where colours suffer are in high-ISO JPEG images, largely thanks to the noise reduction system, which cannot be disabled (only varied in intensity). Those processing Raw images may have better luck removing chroma noise before applying the various colour corrections necessary to bring the image back to life.

Despite some texture at lower sensitivities, noise doesn’t become too great an issue until around ISO 1600 where details begin to be increasingly obscured. Images captured on the JPEG-only ISO 25,600 option struggle to show any significant detail, as noise reduction cannot be disabled here. A comparison with the A65, however, showsthe A57’s noise control to be marginally – but noticeably – better, which isn’t particularly surprising given the larger photosites on the A57’s sensor.

The kit lens supplied with the camera is small, lightweight and, for the most part, optically adequate, but against a high-resolution sensor it becomes easier to see its flaws. Detail improves once the aperture is stopped down, although when an alternative optic is used it becomes clear just how much detail the sensor is capable of resolving. At low sensitivites this is impressive, but noise reduction soon steps as sensitivity is increase. As always, low noise reduction or Raw post-processing is the best way to go.

Although the difference is slight, JPEG images do exhibit better sharpness than corresponding Raw files. Natural subjects show no unsightly sharpening artefacts, although a touch of additional sharpness in post-production does define details without any ill effects. It’s perhaps better to err on the side of caution than over-processing, so it’s difficult to fault the processing here. It’s only at higher sensitivities where things fall apart, as the noise reduction system does what it’s meant to, but not without leaving the familiar watercolour blotchiness. Colour in JPEGs is also good, with some of the casts over neutral areas in certain Raw images rectified.

The a57 records full HD video at 50p using the AVCHD 2.0 codec. When a good optic is used the level of detail in video recordings is excellent, with the AF system immediately bringing subjects into focus. Footage is very smooth and the SteadyShot Inside system noticeably helps to keep the feed stable, while sound quality is also decent with only a little ambient noise picked up. In fact, the only noticeable issue is aliasing when capturing very fine subjects and architectural details, although this is often a problem with such subjects.