I experienced lot of noise while shooting in a nikor 35mm/1.8g lens at 2.2aperture, 250 iso and 1/250 and above shutter. It was day time bit cloudy situation. It was visible if i blew and see the details in light room. My iso100 photos on the same situation did not have the problem. The light was not bad...it was around 3pm but as i said cloudy. It was visible only if i blew and look at the details. Is this common? Whats your experience on the noise level with nikon d5100? I would expect up to 800 it should be decent.