Gunther mentions when the light falls below one stop he adjusts the camera back to zero. I don't understand what that means. How do you tell one stop. I have a D600.

Hi Justin, as long as it's still rather bright outside you can use the metering indicator (you shoot in M). If it gets darker you just press play eventually an observe the histogram of the image. When the "space" to the right of the histogram is big enough (you will have to try a bit to figure that out) you make the adjustment.

Thanks Gunter. So if you are watching the metering indicator, how many bars do you let go until you adjust back to no bars?

That depends, for sunsets I rather underexpose one step. So I start with -1 and adjust when I'm at -2 - but that depends from the situation and your camera.