The goal is to get pleasing face reconstruction, everything follows from that. There's no objectively correct loss function, it's something that is selected bec

The goal is to get pleasing face reconstruction, everything follows from that. There's no objectively correct loss function, it's something that is selected because it has a good effect. A simple example could be sensitivity to color differences: with lighter skin tones there is a fairly large difference between eyebrows and eye features and the person's forehead or cheek. Someone with a pretty dark complexion might have features that are distinguished in a very compressed set of colors. Depending on the loss function a dark complexion face could be essentially flat and featureless. This could be fixed of course... but it requires changing the loss function.