  We present comprehensive cluster membership and g'r' photometry of the
prototypical old, metal-rich Galactic star cluster NGC 6791. The proper-motion
catalog contains 58,901 objects down to g'=24, limited to a circular area of
radius 30 arcmin. The highest precision of the proper motions is 0.08 mas/yr.
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'=22 (M_V=+8) is 4800, corresponding to M_tot=5000 M_solar. 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=4.4 arcmin while
the tidal radius is r_t=23 arcmin). The luminosity function of the cluster
peaks at M_g'=+4.5 and then steadily declines toward fainter magnitudes. Our
data provide evidence that differential reddening may not be ignored in NGC
6791.
