Just wondering about the noise found on the D80 if anyone has ever come across this problem.

I realized that even on ISO 100, the noise found in dark areas of photos appear grainy and noisy. However, this is without long exposure NR turned on.

What is considered a long exposure to the camera? Anything above 1"?
And I think NR reduces sharpness and detail in photos, so I'm wondering if there's anything else I can do to reduce noise without losing detail.

Any opinions and help would be great. :)