A tangency is a point of contact between one shape and another so that they just touch without overlapping. A tangency can also happen when a shape touches the frame of the composition.
This picture by Howard Pyle is full of tangencies:
1. The pirate’s hat with the top of the picture
2. The ship with the shore
3. The chin of the far pirate with the dark hillock
4. The tip of the sash with the head of the digger
5. The tip of the shovel with the frame
6. The head of the kneeling man with the digger’s elbow
7. And the stock of the rifle with the man’s head.
Tangencies cancel out the illusion of depth. They reinforce the flatness of a picture. They’re often regarded as a common beginner’s mistake.
So why did Pyle use them? He was a master of composition and he usually knew exactly what he was doing. The idea of deliberately flattening a picture was very much in vogue at the time Pyle did this picture. His pen and ink works were influenced by Walter Crane and Aubrey Beardsley’s decorative approach to line. Pyle must have wanted the piece to be flat like a playing card.
Do the tangencies help this particular picture? As much as I admire Pyle, in my opinion, they don’t here. They call attention to themselves and get in the way of the larger ideas of story, characters, or mood.