We present comprehensive cluster membership and g ^ { \prime } r ^ { \prime } photometry of the prototypical old , metal-rich Galactic star cluster NGC 6791 .
The proper-motion catalog contains 58,901 objects down to g ^ { \prime } \sim 24 , limited to a circular area of radius 30 \arcmin .
The highest precision of the proper motions is 0.08 mas yr ^ { -1 } .
Our proper motions confirm cluster membership of all main and also some rare constituents of NGC 6791 .
The total number of probable cluster members down to g ^ { \prime } = 22 ( M _ { V } \sim + 8 ) is \sim 4800 , corresponding to M _ { tot } \approx 5000 ~ { } M _ { \odot } .
New findings include an extended horizontal branch in this cluster .
The angular radius of NGC 6791 is at least 15 \arcmin ( the effective radius is R _ { h } \simeq 4.4 \arcmin while the tidal radius is r _ { t } \simeq 23 \arcmin ) .
The luminosity function of the cluster peaks at M _ { g ^ { \prime } } \sim + 4.5 and then steadily declines toward fainter magnitudes .
Our data provide evidence that differential reddening may not be ignored in NGC 6791 .