Mirrors

That old mirror problem cropped up again in The Daily Telegraph: why was one's reflection in the mirror turned around but not upturned. So a letter appeared explaining the phenomenon.
It's not a phenomenon; it's quite simple. The image is not one that looks as if you have done a 180 degree turn if you were, magically, to be able to stand where the reflection is, otherwise your right hand would be on the left and your left hand on the right. Which they are not.
This took me back to my youth at school when we were given for homework the task of drawing our faces as seen in a mirror. I found this rather awkward to do - the mirror kept sliding or whatever - so I thought "The hell with this," and got out a photograph and copied that.
Our art master was a bit of a tyrant, rather frightening, brilliant but scarey. I presented him with my effort: me looking from a page of my artbook out at him.
"You didn't use a mirror, as I wanted," he said.
"Yes, sir, I did," I answered, chest out.
"Why then is your hair parted on the wrong side?"
"Huh!"
In those days the old stick was wielded on hands and bottoms and the old hand was slapped across heads.... I felt the old, hard slap of the hand on the back of my head and was told to get back to my seat; as I did so I felt my work of art, thrown angrilly by the teacher, give me an extra whack on the head.
The question must therefore be: why does a photograph reverse the image left to right but not up and down?
As another letter in The Telegraph put it: before I try to answer that I think I'll reflect on it a while.