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 the Sony Alpha a99's JPEG files have a similar signal to noise ratio to those from the Nikon D600, Canon EOS 5D Mark III and Nikon D800 throughout the sensitivity range. The Sony achieved a slightly stronger ratio than the D800, but falls a little way beneath the other two, with the Canon coming out top.
Raw signal to noise ratio
The signal to noise ratios of the TIFF images (after conversion from raw) from the Sony Alpha a99 show a bit more of a difference than the JPEG images did, with the Sony again falling below the Canon EOS 5D Mark III and above the Nikon D800. It achieves very similar results to the Nikon D600, which marginally beats it at the lower ISO settings.
JPEG dynamic range
JPEG results for dynamic range are a bit more spread out than those for signal to noise ratio, with the Sony Alpha a99 this time producing a stronger dynamic range than the Canon EOS 5D Mark III at the low-to-mid range, before falling behind after ISO 3200. Conversely, the Nikon D600 and Nikon D800beat it at lower sensitivities, but the Sony performs better at ISO 6400 and above.
Raw dynamic range
This chart indicates that TIFF images (after conversion from raw) from the Sony Alpha a99 produce very similar dynamic range results to the Nikon D600, Canon EOS 5D Mark III and Nikon D800. It performs slightly better than the D800, but more or less the same as the other two cameras, overall.