Information Flow and Output Distortion
Input data can come from device sources like digital cameras, image scanners or any other measuring devices. Those inputs can be either monochrome (in which case only the response curve needs to be calibrated, though in a few select cases one must also specify the color or spectral power distribution that that single channel corresponds to) or specified in multidimensional color - most commonly in the three channel RGB model. Input data is in most cases calibrated against a profile connection space (PCS).
One of the most important factors to consider when dealing with color calibration is having a valid source. If your color measuring source does not match the displays capabilities, the calibration will be ineffective and give false readings.
The main distorting factors on the input stage stem from the amplitude nonlinearity of the channel response(s), and in the case of a multidimensional datastream the non-ideal wavelength responses of the individual color separation filters (most commonly a color filter array (CFA)) in combination with the spectral power distribution of the scene illumination.
After this the data is often circulated in the system translated into a working space RGB for viewing and editing.
In the output stage when exporting to a viewing device such as a CRT or LCD screen or a digital projector, the computer sends a signal to the computer's graphic card in the form RGB . The dataset signals only a device instruction, not a specific color. This instruction = then causes the connected display to show Red at the maximum achievable brightness, while the Green and Blue components of the display remain dark . 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.)
Read more about this topic: Color Calibration
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