Friday, November 20, 2009

Light Sources

What are the systems of defining the light sources?
CIE Rating - Based on CIE Publication 51, it is a very strict rating of a light source’s ability to reproduce daylight, in both the visible and ultraviolet spectrums. The first letter provides the rating for
the visible spectrum and the second letter the rating for the UV spectrum. An “AA” rating is the highest and “EE” the lowest. A rating of “BC” or better is acceptable for color matching applications.

To Learn about various light sources Click Here
Color Rendering Index (CRI) - A rating of a light sources ability to reproduce a daylight source. The Color Rendering Index is a scale (0-100) that represents how closely a light source depicts or reflects an object's true color. As a general rule of

thumb, the higher the CRI, the more accurate an object will appear. In the lighting industry, , a rating of 92 or higher is required for critical color evaluation applications.and depicts a truer color.

Color Temperature (AKA Correlated Color Temperature) - A rating of a light sources color output. It is based on the Kelvin scale in which 0 degrees is at Absolute Zero (-273 C) where all motion in a molecule is deemed to stop. The lower the color temperature of the light source, the redder the source will be. Inversely, the higher the color temperature of the source, the bluer it will be. Some common color temperatures, common names associated with them and their associated colors are:
7500K (D75) North Sky Daylight Moderate to Deep Blue
6500K(D65) Average Daylight Moderate Blue
5000K (D50) Equal Energy Daylight White
4100K Various fluorescent sources Greenish
3000K Various fluorescent sources Orangish
200K Tungsten A Red/Yellow
2865K Illuminant A Yellowish Red
2300K Horizon Reddish

What are the standard light sources for textile shade matching?
D75 (Color temperature 75000K) - “North Sky Daylight.”
A bluish colored light source originally used for grading cotton and other evaluation applications.
D65/ F7 (Color temperature 65000K) – “Day Light”
A light bluish colored light source used in color matching applications of paints, plastics, textiles, raw inks, and other manufactured products. It is the only daylight source that was actually measured.
D50 (Color temperature 50000K)
A near white light source used in the evaluation of graphic arts and imaging applications.
Ultra Violet(UV Light)
UV Light energy not normally visible to the human eye, but which is present in natural daylight. UV energy has the ability to excite certain substances (such as optical brightening agents) within a sample causing them to emit light in the visible spectrum, usually in the blue region.
F2( also called F,F02,Fcw,CWF,CWF2)Cool White Fluorescent (CWF Color temperature approx 41000K)
A wide band single phosphor fluorescent source commonly used in commercial lighting applications and office environment..
F11 :- represents a narrow tri band fluorescent at 40000K color temperature.
Warm White Fluorescent & TL830(WWF Color temperature approx 30000K)
A wide band single phosphor fluorescent source used in commercial lighting applications.
TL84(Color temperature approx 41000K)
A narrow band tri-phosphor fluorescent source originally designed for commercial lighting applications.
TL835(color temperature of approximately 35000K )
A narrow band tri-phosphor fluorescent source originally designed for commercial lighting applications.
Ultralume 30 (U30 or 30U Color temperature approx 30000K) - A narrow band tri-phosphor fluorescent source originally designed for commercial lighting applications
Ultralume 35 (U35 or 35U color temperature of approximately 35000K) - A narrow band tri-phosphor fluorescent source originally designed for commercial lighting applications
Source A :-Incandescent and Tungsten Illumination
A typical light bulb found in the home is an incandescent tungsten lamp. It uses a tungsten filament that will glow when electricity is passed through it. These lamps are very common and are used in color match applications where a yellowish to red source is required.
Source C :- it is a historical representation of average sky day light at 67740K .
Tungsten A (3200K )
is used primarily in the photographic, film and video industries where a “whiteish” source and continuous light output are required. It is not commonly used for color matching applications.
Illuminant A(2865K) - is a standardized illuminant described in the international standard, CIE Publication 15.2 and specified for use in color matching applications in ASTM D1729-96. It is used where a yellowishred source is required. It is the predominant source/illuminant used for both instrumental and visual color matching applications.
Horizon(2300K )-
Reddish Source described in older specifications and used for color matching applications Horizon in an outdated standard as an “Incandescent illumination of low correlated color temperature it is not used in instrumental color matching applications.

Name of    CCT (0K)              CRI                    description
A                 2856                       98         Incandescent tungsten
B                 4874                                     Obsolete, direct sunlight at
C                 6774                                     Obsolete, north sky daylight
D50            5003                       98        ICC Profile PCS. Horizon light.
D55            5503                                     Compromise between
                                                                  incandescent and daylight
D65           6504                        98        Television, sRGB color
D75           7504                         96        North sky day light
E               5454                                       Equal energy
F1             6430                                      Daylight Fluorescent
F2             4230                        62        Cool White Fluorescent
F3             3450                         54       White Fluorescent
F4             2940                        51         Warm White Fluorescent
F5            6350                                      Daylight Fluorescent
F6            4150                                       Lite White Fluorescent
F7            6500                        98         D65 simulator, day light
F8            5000                        98         D50 simulator, Sylvania
                                                                F40 Design
F9            4150                                     Cool White Deluxe
F10          5000                                     Philips TL85,
                                                                Ultralume 50
F11          4000                        83         Philips TL84,
                                                                Ultralume 40
F12           3000                        85        Philips TL83,
                                                                 Ultralume 30
Further readings
Light Bulb Colour Temperatures
Explanation of various light sources

FAQs about “Daylight” Lighting

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