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
The 5D Mark III produces the cleanest images of the bunch up to ISO800, at which point it starts to fall short of the Canon 6D and Sony A7. It still manages to produce slightly better results than the Nikon D810 until ISO12800, where the two cameras then even out. It's worth noting that these tests are not always an accurate representation of real-world image quality, so check out the sensitivity and noise images to visually examine noise levels at higher sensitivities.
Raw signal to noise ratio
Analysing the camera's raw output (after conversion to TIFF) we can see that the 5D Mark III scores consistently higher than the D810 at all sensitivities and comes close to the Sony A7's performance. The 6D starts out slightly down on its bigger brother, but regains the lead as sensitivities increase, theoretically producing cleaner images.
JPEG dynamic range
All cameras are capable of very high dynamic range up to ISO3200 with no obvious difference in real world image quality. The 5D Mark III and D810 maintain very close results up to their maximum sensitivities, whilst the 6D and Sony A7 produce high scores up to ISO25600.
Raw dynamic range
Comparing the dynamic range of the camera's raw files (when converted to TIFF) reveals that the 5D Mark III falls slightly short of the competition up to ISO800, where it then claws back ground against the D810. The 6D and A7 are still the cameras to beat though.