We shoot a specially designed chart in carefully controlled conditions and the resulting images are analysed using DXO Analyzer software to generate the data to produce the graphs below.
A high signal to noise ratio (SNR) indicates a cleaner and better quality image.
For more more details on how to interpret our test data, check out our full explanation of our noise and dynamic range tests.
JPEG signal to noise ratio
These results show that JPEGs from the Sony a58 contain reasonable signal to noise ratios, outperforming images from the Canon EOS 650D and Nikon D3200 at every sensitivity setting above ISO 400. The Sony a58's JPEG images contain similar signal to noise ratios to the Sony a57's at lower to mid sensitivities, but the newer camera's images are stronger at ISO 3200 and above.
Raw signal to noise ratio
Signal to noise ratios of the TIFF images (after conversion from raw) from the Sony a58 are much weaker than the JPEGs, relatively speaking, this time performing worse than those from the Sony a57 and Canon EOS 650D at every sensitivity setting, and worse than the Nikon D3200 at every setting except ISO 6400 and 12800.
JPEG dynamic range
As we can see from this chart, the Sony a58's JPEGs show greater dynamic range than the Canon EOS 650D's at every sensitivity but ISO 1600 and 3200. The a58's JPEGs show similar levels of dynamic range to the Nikon D3200 at ISO 100, 200, 1600 and 6400, but the a58 is stronger at other sensitivities. The a58's JPEGs contain similar dynamic range to the Sony a57's at ISO 100 and 200, then the a57's images are stronger from ISO 400 to ISO 6400, but the a58's overtake at the top of the sensitivity range.
Raw dynamic range
TIFF images (after conversion from raw) from the Sony a58 contain greater dynamic range than those from the Canon EOS 650D at ISO 100-800, after which point the scores are very similar. The a58's TIFFs show a similar dynamic range to the Sony a57 and Nikon D3200 at ISO 100 and 200, but after that they fall behind both cameras, only beating the Nikon briefly, at ISO 6400.