Just wanted to back up some of the points begin made in the part of the course I'm presently at.
Different exposures can produce shots that all work in different ways.
1. 13secs exposure.
Taken to show the interior while making the outside to bright to distinguish anything
2. 25secs exposure.
Taken to show the interior in shadow while keeping the detail clear outside the door. Natural draws you to the outside world and the light.
3. 40secs exposure.
This is the best of both worlds shot, the shadows aren't too dark while it doesn't appear to light outside thous losing the detail.
In evenly lit scenes their is generally one 'correct' exposure meaning if you took a number of different exposures from light to dark most people would pick the same one as looking best.