Originally posted by cbaytan I shot say 95% at ISO 100, and always NR off, so I have no clue about when to turn on NR, when to turn off, any enlightenment would be appreciated.
Can.,
To answer your question directly:
1, If you're shooting only at ISO 100, then the High ISO Noise Reduction option doesn't matter. You can turn it on or off: It won't affect your pictures.
2, If you're shooting at higher ISOs (say, 1600), then the option will matter to the jpegs that the camera produces. If you are shooting Raw + JPEG, then the option will make a difference to the JPEG file. Should you use it? It depends. If you want to save yourself time, then turn the option on and let the camera reduce noise in high-ISO images. But if picture detail is more important to you than your time, then do NOT turn it on, or leave it set on the "weakest" setting. Leaving NR off will preserve detail. When you review the photo on your computer, you can then decide whether you want to use noise reduction software to clean up the image.
My real advice is, test it out for yourself. Sounds like it's not really an important question for you, since you shoot mostly at ISO 100. But go ahead, turn the camera up to a high ISO and take some test shots, with noise reduction off, and then with noise reduction on at various strengths. See what you think of the results.
I shoot a LOT at high ISO. I leave the setting OFF. If I find the noise offensive, I adjust it first in Adobe Lightroom. If I don't like the results there, I try either Noise Ninja or Neat Image.
Will