Exposing to the right or this is not your father's camera

[penodr]

JAS is correct. I have read a bunch on this and basically the right side ( light side ) of the histogram has more tonal values than the left side. This is why noise shows up in dark areas of the photo first. When you push the histogram to the right you are using more tonal values to record your data and will have less noise in the image.

Dave

[Greg_Nuspel]

When you expose to the right and there is clipping on the left it is time for HDR.