Humans have poor night vision in comparison to many animals, but a number of different methods have been developed to allow us to see in the dark. These include the use of artificial light, such as torches and lamps, and the use of specialised equipment, such as night-vision goggles.
The ability to see at night is known as scotopic vision. This is different from photopic vision, which is the type of vision we use during the day. Scotopic vision is more sensitive to light but cannot resolve fine details like photopic vision can.
There are two types of night-vision devices: those that amplify existing light and those that create their own light source. Infrared illuminators are often used in conjunction with image intensifier tubes or thermal imaging cameras to provide a clear picture in low-light conditions. Active illumination systems project a beam of infrared light and can be used with either an image intensifier tube or a charge-coupled device (CCD) sensor. CCD sensors are also used in digital cameras and camcorders to record images in low-light conditions.
One common method for enhancing scotopic vision is known as dark adaptation. This involves adjusting to dimmer lighting over a period of time so that the eye becomes more sensitive to light. Dark adaptation can take up to 30 minutes under ideal conditions but may be shorter if there is some residual light present. Once adapted, however, scotopic vision can be lost quickly if brighter lights are introduced – this is why it’s important not to turn on sudden lights when moving around at night!