Noise reduction is set using the 'High ISO NR' option in the 'Shooting' menu. The D300S offers four settings: Off, Low, Normal and High, with Normal being the default.
High ISO Noise Reduction compared
Indicated ISO sensitivity is on the horizontal axis of this graph, standard
deviation of luminosity on the vertical axis.
High ISO Noise Reduction Crops
Noise reduction and fine detail
Noise reduction is essentially a balance between removing noise and retaining fine detail. The JPEG engine in the D300S offers you four different ways of striking that balance, with the 'off' setting doing very little to reduce noise but leaving plenty of detail and the 'high' setting edging towards the other extreme and giving smooth images with little noise but also little detail. Up to ISO 3200, we prefer the 'Low' setting to the camera's default, as it retains plenty of detail and most of the unsuppressed noise is luminance noise (bright and dark 'grain', rather than false-colored, chroma noise), which isn't unpleasant.
To check the effect of noise and noise reduction on low contrast detail we shoot our lovely model framed as shown here, with the new added feature of feathers. The very fine detail in the feathers will help to better judge the effect of noise reduction on fine detail. The ACR crops have noise reduction set to its lowest setting and use the 'Camera Standard' profile to provide more consistent color
Raw vs in- camera JPEG noise reduction low contrast detail comparison
The crops below show how much control you get over the amount of noise reduction applied by the camera's JPEG engine. It's a well-selected range, with a sensible number of steps and a realistic level of noise reduction (the 'Off' setting isn't overly intrusive and we find it hard to imagine you wanting to apply more noise reduction than the 'High' setting).