Subtractive color system

Carbitol Film-forming agent Subtractive color system... 

Subtractive color system A color system based on reflection where colorants absorb or subtract colors used in color laser printing such as CMY. 

Subtractive color photography, 79 283 Subtractive dye imaging systems, 79 284-298... 

Color order systems n. Systems used to describe an orderly three-dimensional arrangement of colors. Three bases can be used for ordering colors (1) an appearance basis, i.e., a psychological basis in terms of hue, saturation, and lightness - an example is the Munsell System (2) an orderly additive color mixture basis, i.e., a psychophysical basis - examples are the CIE System and the Ostwald System and (3) an orderly subtractive color mixture basis - an example is the Plochere Color System, based on an orderly mixture of inks. 

Plochere color system n. A color order system based on subtractive colorant mixture developed by mixing a limited number of pigments in systematically varied proportions. 

A Figure 15 Subtractive colors where the combination of all three produced black. This is also called the CMY system or CMYK system. 

The first instant color photography system, introduced by the Polaroid Corp. in 1963 as Polacolor, used the transfer of subtractive dyes to a receiver sheet to produce a positive image. The incorporated dye-developers, containing a hydroquinone moiety, are soluble in the alkaline activator solution, except where silver development occurs, when they are immobilized as the quinone form. 

Both subtractive and additive color reproduction are utilized in instant color films. Subtractive systems include all of the instant print and large format transparency materials except Polachrome 35-mm sHde films, which are additive. 

In this application, the process analyzer is used in the vis-NIR spectral region to measure the clear top layer on a co-extruded polymer film. The bottom layer is pigmented to an opaque white color and its thickness cannot be determined by this method. Prior to the installation of the fiber-optic spectroscopy system, film samples were measured manually in the laboratory by a subtractive scheme. First, the total thickness of a sample was measured on a manual profilometer. The top layer of the polymer was removed with methylene chloride. The sample was then repositioned on the profilometer as closely as possible to the originally measured spot and the thickness of the second white layer was determined. The thickness of the top layer was then determined by difference. 

For an electronic realization of their system, Land and McCann suggest using logarithmic receptors. If logarithmic receptors are used, then the sequential product turns into a sum. Let log aj be the measured data from the j-th receptor of color band i with i e r, g, h) along the path. Then the ratio between two adjacent receptors can be computed using a simple subtraction. 

Figure 7.17 Moore s hardware implementation of Land s algorithm (Reproduced by permission of IEEE. Moore A and Allman J and Goodman RM 1991 A real-time neural system for color constancy. IEEE Transactions on Neural Networks, IEEE, 2(2), 237-247, March). The output of the camera is smoothed using three separate resistive grids (a). A single resistive grid is shown in (b). The smoothed image is then subtracted from the original image.

The direction in which to project the log-chromaticity differences is unique for each camera. One possible way to compute this direction is to take a sequence of images of a calibration target, such as the Macbeth color checker, which consists of different colored patches. Let us assume that we have n different patches and m images. This will give us m data points p = [prg, Pi, , I for each patch. The data points of each patch all line up approximately. Let Pj be the data point from the / -th patch and k-th image. For each patch, we can move the line to the origin of the coordinate system by subtracting the mean. Let p be the new coordinates with the mean subtracted. 

In quality control of colored objects, production requires more consistency than absolute accuracy. After all, there will generally be a product standard having the correct color to which we may reference the color of parts from the current production run. Since the production part and the product standard will be free from the small errors in accuracy, because any small inaccuracies will be the same in measurements of the batch and the standard and thus will subtract out in the different components. What is needed is an instrument with higher day-to-day objectivity than our visual system, and for such an increase in consistency, one must be willing to give up some of the absolute accuracy. This requires an analog simulation of visual colorimetry. 

To provide more detail to the end user beyond a purity number and a color code, the UV chromatogram and the background-subtracted spectra that correspond to the integrated peaks are written into a format that can be read by a custom browser that resides within the corporate analytical request-and-tracking system. In this way, the end user can view via the intranet the associated LC-MS data by simply clicking on the numeric value for SI, which is reported via the Web page with the other associated profiling data. There is no requirement to have any vendor software on their personal computer (PC). 

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