Art or Porn?

I think I've figured it out with regard to photographic images that depict female nudity.

If it's art, the woman's gaze must be averted, or her eyes or gaze must be concealed or cropped out of the image.

In porn, the woman is showing emotional involvement. Pleasure, revulsion, anger, whatever it is that someone might get off on. As often as not, her eyes look into the camera lens.

Generalizations, I know--I'm certain there may be notable exceptions, but does this jibe with your experience?