Canon 1D Mark IV High ISO NR
Canon EOS-1D Mark IV High ISO Noise Reduction
As noted elsewhere in this review, the Canon 1D Mark IV delivers a noticeable advance in high-ISO image quality over the 1D Mark III. Its four noise-reduction settings also allow you quite a bit of flexibility in choosing how you want to make the trade-off between subject detail and noise levels. The combination of shooting with NR turned Off and using a good noise-filtering program after the fact can produce very clean images with lots of fine detail in them. (And of course, the 1D Mark IV's CR2 files have no high ISO noise-reduction processing applied to them at all, adhering to the true philosophy of RAW shooting.)
See for yourself how the noise reduction works under both daylight and tungsten-balanced lighting. Click on any of the crops below to see the corresponding full-sized image.
The above crops show the effects of the 4 levels of high ISO noise reduction, under the HMI lighting we use to simulate standard daylight. As you can see, the trade-off between detail and noise can easily be seen at the various noise reduction ettings.
To see how Canon 1D Mark IV High ISO JPEGs compare to other professional SLRs (including its predecessor) at default noise reduction settings, see the crops below.
As you can see, the Nikon D3S is the top performer when it comes to high ISOs; not only within this group, but of all digital SLRs at this time. Its easily out-performs the Canon 1D Mark IV, especially at very high ISOs. The 1D Mark IV does however improve on its predecessor, the 1D Mark III, though its default noise reduction appears to be stronger, as can be seen in the smudged red-leaf fabric.
See the RAW crops page to see how the output from the sensors compare independent from any external noise reduction processing.