Light sources for many problems in agriculture and industry require good color rendering; standards are needed for both special and general purpose lamps. Target standards are discussed, and color, relative spectral distributions, and lumen efficiency data are provided for typical incandescent and fluorescent lamps. Data for color samples calculated for triads of light sources studied by an I.E.S. Subcommittee on Color Rendition of Light Sources are used to demonstrate the comparative size and direction of color differences involved in common situations. Problems raised by chromatic adaptation are discussed, as are specifications and standards for sources used for color work in various specialized industries, and the progress being made by I.E.S. and CIE committees on color rendering.
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Except color (see reference 14).
Lumens per watt.
The actual temperature of the tungsten filament is lower than that of a true blackbody when they are a color match, less than 100° at 3000K.
Table IV
Approximate life, color, and light output of seven white fluorescent lamps currently produced by most large lamp manufacturers.
Except color (see reference 14).
Target colors for all except soft white are from Federal Specification W-L-116A, October 6, 1958 (and the proposed ASA C78.376/874, January 1959, in which tolerances are defined in terms of a 4-step MacAdam ellipse). The color of soft white is the average calculated from measurements of the soft white lamps for which curves are shown in Fig. 4.
Hot cathode, instant start lamps are rated 1 or 2 lu/w less than preheat start.
Also called home-lite.
Too far from blackbody locus to assign a correlated color temperature.
Table V
Color differences calculated for 18 samples under a standard reference lamp and two fluorescent lamps, deluxe and standard, for three lamps color-matched at 6500 K.
ΔEN = 1936 Nickerson “Index of Fading” = (C/5) (2ΔH)+6Δ+3ΔC. This is a single number measure for color difference that is based on equivalence (for average viewing conditions) of 3 hue steps (at /5 chroma) to 1 value step, to 2 chroma steps. For special conditions the weighting for value may be varied.
Arbitrary units.
Tables (5)
Table I
Abbot-Gibson data for spectral energy distributions of skylight, 6100 K to limit-blue-sky.
Except color (see reference 14).
Lumens per watt.
The actual temperature of the tungsten filament is lower than that of a true blackbody when they are a color match, less than 100° at 3000K.
Table IV
Approximate life, color, and light output of seven white fluorescent lamps currently produced by most large lamp manufacturers.
Except color (see reference 14).
Target colors for all except soft white are from Federal Specification W-L-116A, October 6, 1958 (and the proposed ASA C78.376/874, January 1959, in which tolerances are defined in terms of a 4-step MacAdam ellipse). The color of soft white is the average calculated from measurements of the soft white lamps for which curves are shown in Fig. 4.
Hot cathode, instant start lamps are rated 1 or 2 lu/w less than preheat start.
Also called home-lite.
Too far from blackbody locus to assign a correlated color temperature.
Table V
Color differences calculated for 18 samples under a standard reference lamp and two fluorescent lamps, deluxe and standard, for three lamps color-matched at 6500 K.
ΔEN = 1936 Nickerson “Index of Fading” = (C/5) (2ΔH)+6Δ+3ΔC. This is a single number measure for color difference that is based on equivalence (for average viewing conditions) of 3 hue steps (at /5 chroma) to 1 value step, to 2 chroma steps. For special conditions the weighting for value may be varied.
Arbitrary units.