When replacing a lens there are some considerations to take into account.
Many of Axis network cameras offer an exchangeable lens and it is important to select a lens suitable for the camera. If a lens is made for a smaller image sensor than the one that is actually fitted inside the camera, the image will have black corners. While, if a lens is made for a larger image sensor than the one that is actually fitted inside the camera, the field of view will be smaller than the lens’ capability since part of the information will be “lost” outside the image sensor.
Every lens is also identified with the f-number, which defines how much light can pass through a lens. The smaller the f-number the better the lens’ light gathering ability. In low-light situations, a smaller f-number generally produces a better image quality. A higher f-number, on the other hand, increases the depth of field.
An iris is used to maintain the optimum light level to the image sensor so that images can be sharp, clear and correctly exposed with good contrast and resolution. If the network camera has been designed with an iris control, the lens needs also to match the same specification.
IR-corrected lenses are very beneficial for cameras that support removable infrared-cut filter. Day/night cameras automatically remove an IR-cut filter in lowlight conditions to take advantage of invisible, near-infrared light.