The challenge when doing surveillance with infrared: Infrared light leads to colour distortion during the day. This is why day/night cameras feature an IR-cut filter which keeps the disturbing infrared light out of the image sensor during the day. When the light falls below a certain level, in contrast, the filter automatically swivels out of the way so that the infrared light does hit the image sensor. At the same time, the camera switches to black/white mode, in which it can use the infrared light optimally.
Our tips for perfect night vision: IR-corrected lenses prevent any out-of-focus images when changing from day to night mode. These lenses automatically correct the varying refraction of different wavelengths and always concentrate the incoming light onto the same pixel. During the day, standard lenses give you the same picture quality as IR-corrected lenses.
The benefits of an IR lens are clear to see in this example of a store: