Color temperature

Clearly, standardized light sources are desirable for color matching, particularly in view of the phenomenon of illuminant metamerism described below. Over the years CIE has defined several standard illuminants, some of which can be closely approximated by practical sources. In 1931 there was Source A, defined as a tungsten filament incandescent lamp at a color temperature of 2854 K. Sources B and C used filtering of A to simulate noon sunlight and north sky daylight, respectively. Subsequently a series of D illuminants was estabUshed to better represent natural daylight. Of these the most important is Illuminant E). ... 

The second category includes BLEVE simulation, in which a pressurized, heated flask containing liquid or liquefied fuel is broken after the desired vapor pressure has been reached, and the released vapor is then ignited. Measurement of fireball diameter, liftoff time, combustion duration, and final height is captured by filming with high-speed cameras. Radiometers are used to measure radiation and temperature is measured by thermocouples or by determination of fireball color temperature (Lihou and Maund 1982). 

Lihou and Maund (1982) used soap bubbles filled with flammable gas which were blown on the bottom of a fireball chamber to form fireballs. A hemispherical bubble was formed on a wire mesh 200 mm above the base of the measuring chamber in order to permit study of elevated sources. The gas bubble was ignited by direct contact with a candle flame, and the combustion process was filmed at a speed of 64 frames per second. The fireball s color temperature was measured. 

Anlauf-farbe, /. (Metal.) tempering color, -temperatur,/. tempering temperature, -zeit, /. filling time (of a pipeline) (Mach.) starting period. 

Typical values of correlated color temperature (CCT) and color rendering index (CRl) for some common electric light sources. 

Roast style weight loss (%) Final color temperature ( F)... 

The spectra have been reduced with the GIRAFFE BLDRS pipeline developed at the Geneva Observatory. EW have been measured with DAOSPEC [2], based on a linelist produced with the Vienna Atomic Line Database (VALD) [3]. Preliminary estimates of the stellar parameters Te//, log g, vt and [M/H] have been obtained from the WFI photometry published by [4] and the color-temperature calibration by [5]. MARCS model stellar atmospheres [6] have been... 

We have first explored the Li line region (670.7nm) for faint stars (bottom of the RGB, the RGB Bump area and the HB, see Fig.l). Data reduction has been done with the GIRAFFE DRS on 123 spectra (signal to noise ratio around 70). The log g have been estimated with a fit of the mean RGB and HB sequences of 47 TUC to a theoretical isochrone (Bertelli et al. 1994), and Teff have been estimated from the (V-I) color-temperature relations (Houdashelt et al., 2000). With [Fe/H]= - 0.65 for 47 TUC, synthetic spectra have been computed from MARCS models (log g= 3.0 TejJ= 4800 K to 5100 K). Li abundances (A Li>0 dex, Li dots in Fig.l) have been derived for 41 stars (with uncertainties of about 0.2dex). 

The proper implementation of the CIE system requires use of a standard illumination source for calculation of the tristimulus values. Three standard sources were recommended in the 1931 CIE system, and these may be presented in terms of color temperatures (the temperature at which the color of a black-body radiator matches that of the illuminant). The, simplest source is an incandescent lamp, operating at a color temperature of 2856 K. The other two sources are combinations of lamps and solution filters designed to provide the equivalent of sunlight at noon, or the daylight associated with an overcast sky. The latter two sources are equivalent to color temperatures of 5000 K and 6800 K, respectively. 

In the Lagrangian approach, individual parcels or blobs of (miscible) fluid added via some feed pipe or otherwise are tracked, while they may exhibit properties (density, viscosity, concentrations, color, temperature, but also vorti-city) that distinguish them from the ambient fluid. Their path through the turbulent-flow field in response to the local advection and further local forces if applicable) is calculated by means of Newton s law, usually under the assumption of one-way coupling that these parcels do not affect the flow field. On their way through the tank, these parcels or blobs may mix or exchange mass and/or temperature with the ambient fluid or may adapt shape or internal velocity distributions in response to events in the surrounding fluid. 

Figure 42 shows the temperatures measured by two-color pyrometry for step changes in temperature compared with the true temperature and calculated temperatures based on the response characteristics of the detectors (time constant = 0.311 s). The response speed of the detectors in this case was too slow to follow the actual temperature decrease, but the temperature rise is reasonably well detected. Spjut and Bolsaitis reported that two-color temperatures are unreliable when the optical properties of the microparticle change during the experiment, but they showed that single-wavelength temperatures can yield consistent results and, with some caveats, are adequate for particle temperature measurement. 

The spectral classes are further subdivided into ten categories given by numbers 0-9, with luminosity, color, temperature, and stellar mass increasing from 0 to 9. 

These earliest UV observations can be combined with optical data to derive a bolometric light curve (Blanco et al. 1987). Although the color temperature was only of order 15,000 K at the time of our first data, it must have been far higher... 

Using the line strengths and parameters given in Table 1, and the solar abundances for So, Fe, Sr, and Ba listed by Cameron (1982), we have oomputed the relative abundances of these elements with respect to their solar values as a function of exoitation temperature from eqn, (4), and the results are shown in Figure 1. The corresponding color temperature for the supernova at this time has... 

This value occurs for a temperature Texo = 5,100 K, which is essentially the same Texc inferred from the color temperature. Thus, we take as the derived abundances for the supernova envelope the following values based on the observed absorption line strengths [Sc/Fe] - 0.90, [Sr/Fe] = 0.75, and [Ba/Fe] 0.55. 

In the theoretical visual luminosity, there remain uncertainties. The supernova atmosphere is scattering dominated so that the color temperature may be significantly higher than the effective temperature (Shigeyama et a1. 1987 Hoflich 1988), i.e., diluted black body radiation is emitted. The bolometric correction is sensitive to the color temperature because it is as high as 4 - 6 x 104 K. More careful calculations would be required to obtain accurate constraints on Rq and E/M. 

The relatively weak dependence on the ratio Ktat/ i abs suggests that the modification to our calculated results will not be great except at very early times. The effective temperature calculated for Model 10H, for example, is, without modification, within 15% of the values inferred from the spectrum (Suntzeff, private communication) on days 1.14 (13,600 K), 1.51 (12,700 K), and 1.85 (11,690 K). Figure 5 illustrates the effect for K<0 0.3, and 0.1. The latter corresponds to a color temperature one third greater than the effective emission temperature. Karp et a1. (1977) have considered the effect of Doppler broadened lines on the bound-bound opacity. For typical photospheric densities (1012 g cm-3) and temperatures (5000 K to 50,000 K) the line opacity is approximately 20% to 200% that of electron scattering (see their Table 3). This should keep the color temperature within about 20% of the effective emission temperature. 

Fig. 5 - Correction to the early visual light curve of Model 10H for the fact that the color temperature does not equal the effective emission temperature for an atmosphere whose opacity is dominantly due to electron scattering. The three curves from top to bottom have the nonconservative opacity equal to 1, 0.3, and 0.1 of the electron scattering opacity. 

B. The comparison is made under an artifical light source of approximately 150 candela intensity and a color temperature of 7500 degrees Kelvin i 200 degrees. 

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. 

The International Commission on Illumination (CIE) International Commission on Illumination (CIE) has defined a set of standard illuminants to be used for colorimetry (International Commission on Illumination 1996). Figure 3.21 shows the CIE illuminants A, C, Z>5o, Z>55, Z>65, and D15. Illuminant A represents the power spectrum of light from a black-body radiator at approximately 2856 K. If this type of light is required for experiments, a gas-filled tungsten filament lamp that operates at a temperature of 2856 K is to be used. Illuminant Z>65 represents a phase of daylight with a correlated color temperature of approximately 6500 K. The CIE recommends to use this illuminant wherever possible. 

Similarly, illuminants D o, D55, and >75 with correlated color temperatures of approximately 5000 K, 5500 K, and 7500 K respectively were also defined. These illuminants should be used whenever cannot be used. 

Judd DB, MacAdam DL and Wyszecki G 1964 Spectral distribution of typical daylight as a function of correlated color temperature. Journal of the Optical Society of America 54(8), 1031-1040. 

For instrumental evaluation spectrophotometers are preferred. The colorimetric values obtained depend on the instrument and its instantaneous state (chiefly the sample illumination conditions) and must be controlled by suitable methods [174], The influence of the instrument can be eliminated by conversion to the standard illumination D 65, representing daylight with a correlated color temperature of 6504 K [175]. The degree of whiteness and the tint values can then be calculated from these colorimetric data with appropriate formulas. A selection of currently used whiteness formulas can be found in [176,177], For recent attempts at standardizing the assessment methods for white objects, see [9,178-185],... 

Orbiting Carbon Observatory Ocean Color Temperature Scanner Ozone Destroying Substance... 

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