
Originally Posted by
Daniel Browning
It would not be a simple linear rate change over time; the exposure variance would be logarithmic around sunset, and it would vary by the time of year (length of sunset), percentage of cloud cover, haze, horizon lines, etc.
Furthermore, changing the shutter speed would make movement in the frame go from strobe-like to smooth, so it would be better to modify the sensor amplification instead of (or in combination with, at much longer intervals) shutter speed. In other words: start at ISO 50, then 51, 52, etc. Not actual analog amplification, of course, but in the metadata for a software push.