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.
We have compared the Canon 5D Mark III's raw files (after conversion to TIFF) with those from the Nikon D800. We processed the raw files with and without noise reduction, for the Canon 5D MK III we did this using the Digital Photo Professional software supplied with the camera, but for the D800 we used Nikon's Capture NX2 which is an optional extra costing around £135 or $132.
Raw (after conversion to TIFF) signal to noise ratio
This chart shows that the Canon 5D Mark III has a better signal to noise ratio across most of the sensitivity range, indicating that images are cleaner at pixel level. Both cameras produce images with a lower signal to noise ratio when noise reduction is turned off. For much of the sensitivity range the 5D MK III's raw files (after conversion to TIFF) with noise reduction turned off are a close match for those from the Nikon D800 with noise reduction set to its default level.
Raw (after conversion to TIFF) dynamic range
Up to around ISO 400 the Nikon D800 leads the way for dynamic range indicating that it is capable of reproducing subtle tonal gradations in highlight and shadow areas. At mid to high sensitivity settings the Canon 5D Mark III's raw files (after conversion to TIFF) have a greater dynamic range than the D800's.