The angle problem of  Infrared light

The luminescence conversion of infrared lamp is fixed( it is more like ir led strips), if want to large lighting angle, it will sacrifice irradiation distance, on the contrary, for the irradiation distance will lost angle! Selection of infrared light angle is a very important thing.  The use of large angle of the infrared light with small angle LED lens, the phenomenon of waste light is existing.
For example, a lamp infrared light, emitting angle is 80 degrees (equivalent F3.5mm angle lens), if with F35mm LED lens, then there will be ninety-nine percent of the   light  outside the camera field, , that is to say, only one percent of the light is useful, others are wasting. The use of small angle infrared lamp with large angle lens, light angle is small, the emergence of a spot in the image center, around the relatively low brightness, this effect is usually said “flashlight”.

In general, the infrared light angle and other the angle of a LED lens is favorable, with the most scientific. Anyway better results can get ideal effect, wide angle, lower cost.