This is a particularly interesting close-up shot from The 400 Blows. This photo is very powerful and gives you a bit of an uneasy feeling. This shot was when Antoine caught his mother kissing another man when skipping school. This shot captures this beautiful woman's thoughts. It is striking to me because she appears sneaky, untrustworthy, and insensitive. Up until this point in the film the mother was very cold to her son and husband. This photo allows you to understand why the family had a difficult relationship at times. The mother does a lot of the blaming on her son, when in reality she is the one at fault. After she sees that her son saw her kiss this man, she tries to bribe him to get good grades. When capturing this shot, Francois Truffaut was very particular in the symbolism he wanted to evoke to the viewers.
On another note, being a woman in 1959 was very difficult. My guess is that this woman felt trapped or unhappy in her marriage. Because it was frowned upon to divorce during this time, the woman fulfills her emptiness in others, even if it breaks morals.