Nikon D300 Complete Manual page 416

Note: If you're shooting JPEG or TIFF images, the above
parameters are used to apply sharpening to the actual pixel
data that is saved in your image file. If you shoot NEF, the
"tag" for the sharpening value is stored in the EXIF data and
the data is left untouched. However, note that programs
such as Nikon Capture NX use the camera tags as the
default setting for conversion, so unless you override the
sharpening value in your NEF conversion program,
sharpening may be applied by the program! That's one
reason why I sometimes suggest setting sharpening to 0 if
you shoot NEF images.
Sharpening is usually applied twice to images (only one of
these potentially occurs in camera). The first sharpening is
used to compensate for the anti-aliasing (fuzziness) that is
inherent in digital image acquisition due to high frequency
sampling. I'd argue that this sharpening should be minimized
as much as possible.
A final sharpening should only be applied to an image when
you know the reproduction size. For example, I often use a
Radius value of 0.3 to 0.5 when sharpening small images
destined for the Web or computer view. When printing on an
Epson inkjet printer, such as the 1800 or 2400, I sometimes
use Radius values as high as 0.8 to 1.2, since I know that the
ink tends to spread upon contact with the paper I use,
masking the sharpening effect somewhat. (The dot gain on
most consumer Epson printers with regular ink and papers is
about 30%.) Another photographer I know applies Photoshop
Unsharp Mask values of 4, 50, 4 for the D300 (Radius,
Amount, Threshold). What you use depends on your output
device and the way you balance visual impact with artifacts.
Many photographers also believe that it's incorrect to apply
sharpening to color image data (among other problems, the
colors can shift due to the methods used to lighten or darken
edges). These folk tend to advocate switching the image mode
to Color Lab (Adjust/Mode/Color Lab in Photoshop),
applying sharpening only to the luminosity layer, then
Thom Hogan's Complete Guide to the Nikon D300
V1.02
Page 416