Visual Evaluations

Whether a color evaluation is visual and/or instrumental, the evaluations and measurements must be accurate, precise and reproducible! In order to accomplish these goals the following must be satisfied:

The Observer and Visual Evaluations:

• Sample viewing surfaces must be specified.
• Viewing geometry must be specified.
• Sample surroundings must be identified and specified.
• The viewing light source must be specified.
• Communicate and agree upon all aspects of the assessment.

Viewing light source selection is one of the first issues to be addressed in color perception. The source of illumination for samples can come from any of the sources listed in the table below. You need to select one or more of these sources other than outdoor skylight. These sources can be identified by their Correlated Color Temperature, as measured in degrees Kelvin. Any noncombustible material, which is known as a black body when heated to a given Kelvin Temperature will produce a specific quantifiable radiation regardless of the black body’s composition. This radiation by a black body is totally reproducible. Artificial sources attempt to mimic that black body radiation. Each light source has its own Spectral Power Distribution (SPD) curve, which indicates the amount of light energy present in the source at each wavelength.

Lamp Designation	CIE Chromacity Coordinates		Correlated Color Temperature – Degrees Kelvin	Color Rendering Index
	x	y
Cool White	0.373	0.385	4250	62
Cool White DX	0.376	0.368	4050	89
Warm White	0.436	0.406	3020	52
Warm White DX	0.44	0.403	2940	73
Daylight	0.316	0.345	6250	74
Macbeth D50 Fluor	0.34	0.36	5150	93
Macbeth D65 Fluor	0.313	0.324	6520	94
Macbeth D75 Fluor	0.299	0.31	7550	95
TL84	0.375	0.38	4100	85
UltraLume 30	0.44	0.406	3000	85
Horizon	0.492	0.416	2300	100
Tungsten	0.424	0.399	3190	100
Mercury Vapor	0.373	0.415	4430	32
Metal Halide	0.396	0.39	3720	60
Xenon	0.324	0.324	5920	94
High Pressure Sodium	0.519	0.418	2100	21
Low Pressure Sodium	0.569	0.412	1740	-0.44

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