Understanding Cameras and Lights

It is crucial for photographers, novice and experienced alike, to know how their digital camera meters light. This is needed for achieving consistent and concise exposures. Metering is the camera's nervous system that determines shutter speed and aperture, based on lighting conditions and ISO speed (standard for measuring the speed of film or how fast it responds to light). Each of the different metering options responds differently to lighting conditions. In a given lighting condition, some may excel while others fail.

Nearly all objects emit, reflect or transmit light, and this ability is measured through the electromagnetic (EM) spectrum, the frequency range of an object's EM radiation. The frequency is measured in wavelengths, which range from the size of an atom to a thousand kilometres. The visible or optical spectrum is one that can be seen with the naked eyes. Long wavelengths like radio, microwave and infrared (IR) have low frequency while short wavelengths like ultraviolet (UV), x-ray and gamma have high frequency. If all objects reflect the same light, it would be great. But in reality, different objects have different reflectance; thus the need for standardising in-camera metering.

In vision applications that incorporate camera technology, the optical fields of visible IR and UV are popular. They usually make use of specialised optics, filters, and lighting solutions. IR camera technology is quite common in military applications, while UV camera technology is widely used in machine vision and industrial imaging. IR is a wavelength longer than visible light, but shorter than radio waves; UV is shorter than visible light, but shorter than x-ray. Most cameras have wavelengths that range near IR or near UV, plus wavelength enhancers. Such devices offer countless imaging solutions to various sectors.