each of the three channels (that is, exactly what will be output, in terms of light, for the given values of red, green, and blue). This may be expressed by the following diagram:
Figure A-2Model of Standard Display Device
Here, the input RGB values are first modified by the appropriate transfer function (γR, γG, or γB); this operation may be viewed as being performed by three look-up tables (LUTs) of the appropriate width and depth. The modified RGB values (R′, G′, and B′) are then mapped to the resulting output light levels of the correct intensity and color. This may be viewed as a matrix multiplication operation (A) involving the R′G′B′ values and the appropriate XYZ tristimulus values for the specific display device primaries, luminance, and white point in question:
Figure A-3Matrix Multiplication of Input Values
In essence, the R′, G′, and B′ values may be seen as “gain controls” on three light sources whose peak outputs are described as (XR,YR,ZR), (XG,YG,ZG), and (XB,YB,ZB). The display device itself – in this case, the LCD module used in the LP2480zx monitor – of course has its own native characteristics which may be modeled as described above. The problem of emulating a different (presumably, standard) output device characteristic is then one of adding a “transform” block (T, in the diagram below) which will modify this native characteristic such that the overall system emulates the desired performance. In terms of the above diagram, if the combination of γS and AS represent the desired standard characteristic, it is the function of the transform block T to correct the native display characteristics (γD and AD) such that the output (TD) of this system matches that of the standard device, for the same input values:
Color Space Emulation 35