Here is a link to the exact camera that I have mounted. You are correct with the sidewalk being approx 15ft away. I will go by my parents tonight and turn the camera in different positions and see what happens. I have the same cameras on my house and no light and do not have this problem. Here are the specs from the camera I have since it will not let me post a link.
Features
Varifocal 4 to 9 mm lens
1/3 inch Sony Super HAD CCD Sensor
420 TV Lines
125ft. IR view distance
Built in 48 IR LED
Exterior adjustments for focus & zoom (no need to remove housing)
Wall mount only
Cable management bracket
Specifications
TV System: NTSC
Image Sensor: 1/3-inch Sony Super HAD CCD sensor
Resolution: 420 Lines
Video Output: 1.0 Vp-p 75 Ohms
Min. Illumination: 1 LUX (0.2 LUX with IR)
Shutter Speed: 1/60~1/100,000 sec. for NTSC
Backlight Compensation: Auto
White Balance: Auto
Gamma Correction: > 0.45
S/N Ratio: Over 50dB at AGC off
Waterproof Rating: IP55
Power Supply: DC12V 1 amp
Operating Temperatures: -4°F ~ 122°F (-20°C + 50°C)
Dimensions: 85mm (diameter) X 124mm (length) [3.35in(D) X 4.9in(L)]
Weight: 680g (1.5 lbs.)