Color correction

Color contamination is another factor that needs to be considered. For example, a small amount of cyan commonly contaminates magenta. Thus, adding magenta to color-correct an image also adds cyan, which must be removed for compensation. 

Lighting. An important appHcation of clear fused quartz is as envelop material for mercury vapor lamps (228). In addition to resistance to deformation at operating temperatures and pressures, fused quartz offers ultraviolet transmission to permit color correction. Color is corrected by coating the iaside of the outer envelope of the mercury vapor lamp with phosphor (see Luminescent materials). Ultraviolet light from the arc passes through the fused quartz envelope and excites the phosphor, produciag a color nearer the red end of the spectmm (229). A more recent improvement is the iacorporation of metal haHdes ia the lamp (230,231). 

Dispersibility. Pigments modified with a dispersion additive take less time and energy to disperse in a coating (12,44). The equipment for blunging is simpler and less expensive than bah. mihs. Color correction is simplified and settling is minimized. Color strength in letdowns is often improved... 

Polyvinyl chloride/Polyvinyl acetate Good prevent yellowing. High-molecular-weight organotin stabilizers improve radiation stability color-corrected radiation formulations are available. Less resistant than PVC. 

White-colored correction fluids like Liquid Paper and White-Out contain the pigment titanium dioxide (Ti02) and the volatile solvent 1,1,1-trichloroethane or methyl chloroform (CCLCFL). The volatile substances in the correction fluid contribute 50% of the total volume of the product. Correction fluid thinner is simply 100% 1,1,1-trichloroethane solvent,I added to redissolve any solidified titanium dioxide. 

Apochromat Microscope objective that has better color correction than the much more common achromat objectives corrected chromatically for two wavelengths of light (red and blue). Apochromatic objectives are corrected chromatically for three colors (red, green and blue) and spherically for two colors, which practically eliminates chromatic aberration. 

On both sides of the resonance region n increases with increasing frequency, which is called normal dispersion. Only in the immediate vicinity of the resonance frequency does n decrease with frequency, so-called anomalous dispersion. Such a reversal of dispersion, if it occurred in transparent regions, would provide a much-needed material for designing color-corrected lenses. Unfortunately, anomalous dispersion occurs only in regions of high absorption where no appreciable light is transmitted. 

Footcandle Meter. A color-corrected illumination meter calibrated in footcandles. 

The concentrations are expressed as integration units of the peak areas (counts), the factor 1.7 being the ninhydrin color-correction factor. 

A color correction may also be achieved by using filters. Table 3.1 shows the type of filter used by professional photographers to achieve accurate color reproduction. The required filter depends on the type of illuminant and also on the type of film. The type of light source can be described using the temperature of a black-body radiator. A black-body radiator is a light source whose spectral power distribution depends only on its temperature (Jacobsen et al. 2000). The color temperature of a fight source is the temperature of a black-body radiator, which essentially has the same spectral distribution in the visible region. The concept of a black-body radiator is formally introduced in Section 3.5. 

Rahman et al. (1999) extended the algorithm of Moore et al. They use a Gaussian to compute the blurred image and perform color correction on multiple scales. This method is not only used for color constancy but also for dynamic range compression. Output color o, is computed as... 

By integrating such a color constancy algorithm directly into the imaging chip, we would obtain a color corrected image before the data is stored in memory. No external processor would be required. Efforts to create artificial retina chips have already tried to include functions such as edge detection, elimination of noise, and pattern matching directly into the image acquisition chip (Dudek and Hicks 2001 Kyuma et al. 1997). 

Figure 11.12 Shifted color gamut (a). The white point lies at the position a. A color correction can be performed by shifting the colors toward the gray vector (b). Now the color gamut is centered around the gray vector. In order to fully use the available color space, we can increase the color gamut as shown in (c).

Color correction on multiple scales, no gain factor. 

Funt BV and Lewis BC 2000 Diagonal versus affine transformations for color correction. Journal of the Optical Society of America A 17(11), 2108-2112. 

Moroney N and Sohel I 2001 Method and apparatus for performing local color correction. European Patent Application EP 1 139 284 A2. 

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