The top row of images came from the narrow-angle camera between 17:00 and 18:28, after which the narrow-angle camera went into safe mode. The rest are from the wide-angle camera.
The third row appears bright because Rosetta passed nearly between the Sun and the asteroid, seeing the asteroid at near zero phase; the brightness is from the opposition effect. The center image on the fourth row was taken at closest approach at 18:39:13. The final image in the series was taken at 18:49.