Spectral reflectance factors

In Eqs. (7)—(10), 5(A) is the spectral power distribution of the illuminant, and R A) is the spectral reflectance factor of the object. Jc(A), y(A), and 5(A) are the color-matching functions of the observer. In the usual practice, k is defined so that the tristimulus value, Y, for a perfect reflecting diffusor (the reference for R A)) equals 100. Using the functions proposed by the CIE in 1931, y(A) was made identical to the spectral photopic luminous efficiency function, and consequently its tristimulus value, Y, is a measure of the brightness of objects. The X and Z values describe aspects of color that permit identification with various spectral regions. 

Pigments and coatings may be unambiguously characterized by their spectral reflectance curves q (A) or spectral reflectance factor curves / ( ) (Fig. 3). The reflectance spectrum q (A) or R (A) and hence the color properties can be almost completely derived from physical quantities [1.15] (Fig. 4) ... 

Materials pigmented with interference pigments can be characterized. by color data obtained from spectral reflectance factors at specific illumination and detection angles (15). Similarly, color information for metal flake pigmented materials, has been obtained on... 

When considering light of a certain spectral energy distribution falling on an object with a given spectral reflectance and perceived by an eye with its own spectral response, to obtain the perceived color stimulus it is necessary to multiply these factors together as ia Eigure 6. Standards are clearly required for both the observer and the illuminant. 

Weissman, L., 1998. Factors affecting the production of endogenic ethylene, changes in spectral reflectance response, membranes and chlorophyll integrity and the composition of mineral elements in the lichen Ramalina lacera (With.) J.R. Laund., M.Sc. thesis, Tel Aviv University (in Hebrew). 

Once a reflectance curve is obtained spectrophotometrically, the measured information is mathematically transformed according to standard conventions, into the numbers used to describe the color of the sample. In practice, a standard observer and standard illuminant are selected based on test methods defined by the Commission International de I Eclairage (CIE). Calculation procedures involve the numerical integration of the product of the spectral power distribution S(l) of the light source and the reflectance factor R(l). Reflectance factors represent the percentage of light reflected by the sample at each wavelength. 

Weighting factors published in the American Standard Test Method, ASTM E 308-85, were used to calculate tristimulus values from spectral reflectance data. The weighting fac-... 

The radiation emitted and picked up by the antenna depends on three factors emission, reflection, and transmission. The energy emitted is proportional to eA and to (real temperature of object) and is affected by the spectral reflectance, pA, the transmittance, tA, and finally by the consequences of radiations incident on the object, Ts coming from the sky and coming from the clouds, which gives, for the value of the brightness ... 

Several factors affect the bandshapes observed ia drifts of bulk materials, and hence the magnitude of the diffuse reflectance response. Particle size is extremely important, siace as particle size decreases, spectral bandwidths generally decrease. Therefore, it is desirable to uniformly grind the samples to particle sizes of <50 fim. Sample homogeneity is also important as is the need for dilute concentrations ia the aoaabsorbiag matrix. 

The same set of measurements for DNP-Leu as selectand and 0-9-allylcarbamoyl-10,11-dihydroquinidine as selector displayed a considerably different picture. While no indication for H-bond formation between the aromatic a-amino group and the carbamate of the selector could be deduced, the IR spectra of free and respective complexed forms suggested the occurrence of K-K-interactions of the DNP group as evidenced by a shifted C=C stretching vibration from 1594 to 1588 cm in the stronger bound 5-complex (force constant weakened due to delocalized electrons). This type of shift was not found in the weak TJ-complex, but in the corresponding 5-complex of DNP-N-methyl-Leu as well. The spectral data nicely reflect the binding relationships in HPLC where both DNP-Leu and DNP-N-methyl-Leu are well separated with comparable separation factors, but with an elution order that is opposite compared to DNB-Leu. 

Near Infrared Reflectance Analysis (NIRA) is in use at over 5000 sites for the analysis of multiple constituents in food and other products. The technology is based upon correlation transform spectroscopy, which combines NIR spectrophotometry and computerized analysis of a "learning set" of samples to obtain calibrations without the need for detailed spectroscopic knowledge of factors being analyzed. The computer can obtain spectral characteristics of the analyte (based upon a correlation with data from an accepted reference analysis) without separation of the sample s constituents. 

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