Image Detail
The sequences below illustrate the Nikon D3x (right column) and Canon 1Ds Mark III’s (left column) respective balance of noise and detail throughout their sensitivity range. Note how the noise becomes increasingly pronounced, while the discernable detail in the hair wanes as the ISO is pushed.

The detail samples are 100% crops. The original images were shot in RAW and converted to JPEGs using a neutral (“all off”) conversion in Adobe Camera Raw.
 

Canon 1Ds Mk III - ISO 100	Nikon D3x - ISO 100
Canon 1Ds Mk III - ISO 200	Nikon D3x - ISO 200
Canon 1Ds Mk III - ISO 400	Nikon D3x - ISO 400
Canon 1Ds Mk III - ISO 800	Nikon D3x - ISO 800
Canon 1Ds Mk III - ISO 1250	Nikon D3x - ISO 1250
Canon 1Ds Mk III - ISO 1600	Nikon D3x - ISO 1600