of the display remain dark [0]. The resultant color being displayed, however, depends on two main factors: the phosphors or another system actually producing a light that falls inside the red spectrum; the overall brightness of the color resulting in the desired color perception: an extremely bright light source will always be seen as white, irrespective of spectral composition. Hence every output device will have its unique color signature, displaying a certain color according to manufacturing tolerances and material deterioration through use and age. If the output device is a printer, additional distorting factors are the qualities of a particular batch of paper and ink. The conductive qualities and standards-compliance of connecting cables, circuitry and equipment can also alter the electrical signal at any stage in the signal flow. (A partially inserted VGA connector can result in a monochrome display, for example, as some pins are not connected.) Color perception Color perception is subject to ambient light levels, and the ambient white point; for example, a red object looks black in blue light. It is therefore not possible to achieve calibration that will make a device look correct and consistent in all capture or viewing conditions. The computer display and calibration target will have to be considered in controlled, predefined lighting conditions. Calibration techniques and procedures The most common form of calibration aims at adjusting cameras, scanners, monitors and printers for photographic reproduction. The aim is that a printed copy of a photograph appear identical in saturation and dynamic range to the original or a source file on a computer display. This means that three independent calibrations need to be performed: The camera or scanner needs a device-specific calibration to represent the original's estimated colors in an unambiguous way. The computer display needs a device-specific calibration to reproduce the colors of the image color space. The printer needs a device-specific calibration to reproduce the colors of the image color space. These goals can either be realized via direct value translation from source to target, or by using a common known reference color space as middle ground. In the most commonly used color profile system, ICC, this is known as the PCS or "Profile Connection Space". Camera The camera calibration needs a known calibration target to be photographed and the resulting output from the camera to be converted to color values. A correction profile can then be built using the difference