At an angle of 90 degrees from the vertical, the light is shining directly outwards, making it impossible for onlookers to see any criminal activity.

 

At 67^o, the problems persist as at 90 degrees, making your "security" light a serious security risk.

 

The floodlight has an opening angle of 72 degrees, and so the light needs to be angled at less than half that (i.e. less than 36^o) to illuminate the background (in this case, a wall).

At 22^o, the floodlight begins to become a security aid. The house wall is illuminated, and so any intruder is highlighted against the background even if (as in this case) the background (i.e. the gate) is dark. However, when standing close by, the light source is still visible, which impedes the ability of a nearby witness to identify an intruder.

Pointing a floodlight directly downwards is the best solution. The background wall is illuminated, and the bulb of the floodlight is no longer visible, making it easier on the eye. However, the floodlight is still over-powered (in this case, a 500W bulb); such a bulb will always generate strong shadows for people to hide in. The best overall solution is a floodlight pointing directly downwards whilst using a low powered bulb (60-120W will aid onlookers, without generating glare).