Color density light source

Table 3.1 Filters that should be used for accurate color reproduction. The filter depends on the light source as well as the type of film used. The filter numbers are references to Kodak Wratten filters. The first digit designates the color and the letter the density of the filter (data from Hedgecoe (2004)).

Lovibond color system A system of color specification by means of numbers proportional to the optical densities of three glass filters (yellow, red, and blue) required to modify a standard light source (such as daylight or incandescent lamp light) to produce a color match. The carefully calibrated glasses should be used as described by the... 

Rocks consisting of the minerals discussed above, in combinations expected for mantle sources or residues, are found at Earth s surface. These rocks have high densities, high Mg and low silica concentrations, are rich in dark colored olivines and pyroxenes, and are referred to as ultramafic. Frey et al. (1971) and Philpotts et al. (1972) analyzed a variety of such rocks for lanthanides to determine whether their distributions would be like those in chondrites or deficient in light lanthanides relative to chondrites. Such a deficiency would be consistent with origin of those rocks in the mantle as well as with the complementarity of distributions for crust and mantle as described above. Very few of the ultramafic rocks analyzed had those characteristics some typical distributions are shown in figs. 21.15-17. 

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