Winter Sunrise over Boston Skyline and Icy Charles River with Water Blur and Buoys

I have found when doing really long exposures facing either a sunrise or sunset directly , I need to factor in the change in ambient light into my exposure calculation. But many times I just calculate an exposure with a safe histogram, and then always have the option to cut the exposure length short while observing the light during the exposure. This photo is a good example of cutting the exposure short even after factoring in the change in ambient light into the exposure calculation. This exposure was over 6 mins in length.

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