My favorite portrait photographer is Richard Avedon. This image precisely defines what the act of portraiture consists of at its core.

“For hours she danced and sang and flirted and did this thing that’s – she did Marilyn Monroe. And then there was this inevitable drop. And when the night was over and the white wine was over and the dancing was over, she sat in the corner like a child with everything gone. I saw her sitting without expression on her face and I walked towards her but I wouldn’t photograph her without her knowledge of it. As I came with the camera, I saw that she was not saying no.”

Richard Avedon

https://www.avedonfoundation.org/