Does Nikon D800 apply noise reduction even when High ISO NR is turned off in camera shooting menu? That seems to be what the Nikon D800 User Manual says as shown in the screen capture below. Does this affect only JPEG/TIFF output or NEF raw image as well?
Most likely not. It may not even affect the jpeg output from the camera.
The following chart shows JPEG file size vs ISO for images (Imaging Resource samples) shot with different NR settings (NR0=Off, NR1=Low, NR2=Normal, NR3=High). I also included the data for JPEG files converted using Nikon Capture NX 2 from NEF raw images with default NR setting and with NR turned completely off in the Develop module.
With higher ISO, the image will contain more noise. The noise makes it difficult to compress the image data therefore file size increases. If noise reduction is applied to the image data, the file size will be reduced. The more noise reduction is applied, the smaller the file will be.
The chart above shows that without noise reduction, the JPEG (exported from Capture NX 2 at 100% quality) file size increases smoothly with increased ISO. However the exported files have a sharp size reduction at ISO 1600 as shown in the green line. Even though the High ISO NR setting is turned off, Nikon Capture NX 2 still gets a hint to apply noise reduction. It is not hidden though. Under Develop->Camera Settings -> Noise Reduction, Color Noise Reduction is by default set to 3%. At the same time, the out-of-camera JPEG file does not show such a file size trend.
It appears that the manual is not very accurate. Can this be a software bug?
Keywords: D800, D800E, ISO, Nikon, Noise