Overtaking another 737 flying 2000ft (600m) below us. Normally the 737 cockpit windows are such poor quality that zooming is impossible.
The different layers blur the image so much that taking photos is just not possible, as you can see happening just below the aircraft; the little lightbrown spot is blurred too.

Today... the angle through the window was just perfect and allowed me to get a sharp snapsnot of the bird below us.