First, night vision ratings are assigned to cameras after they are tested under the best possible circumstances. Most customers will get about two-thirds of the rating in their environments.
Here are some things to test to make sure that you are getting the most out of the night vision:
Check that the IR lights are illuminated. You should see a glow around the lens at night or when you cup your hands around the camera lens. If the lights are not illuminating, but you do have a daytime picture, the issue could be related to power or it could be a defective camera.
Power can degrade over longer cable runs. Runs over 165 feet may need more power.
Cameras with a night vision distance of 80 feet or more require 1 Amp, and cameras with a night vision distance of less than 80 feet require 0.5 Amp. Make sure that the power supply you are using will allocate the appropriate amperage for the camera.
Make sure the camera is aimed at a downward angle. The IR light needs to bounce off something to create an image. Imagine a flashlight aimed parallel to the ground in an open field or parking lot. You would not be able to see much. If you angle the flashlight down toward the ground, you will be able to see where you are going. The same principle applies to the IR light from the camera.