Color Temperature of light sources

Approximate Correlated Color Temperature for Various Light Sources

Source	Degrees K
Artificial Light
Match Flame	1700
Candle Flame	1850
40-Watt Incandescent Tungsten Lamp	2650
75-Watt Incandescent Tungsten Lamp	2820
100-Watt Incandescent Tungsten Lamp	2865
500-Watt Incandescent Tungsten Lamp	2960
200-Watt Incandescent Tungsten Lamp	2980
1000-Watt Incandescent Tungsten Lamp	2990
3200-Degree Kelvin Tungsten Lamp	3200
Molarc "Brute" with Yellow Flame Carbons & YF-101 Filter (approx.)	3350
"C.P." (Color Photography) Studio Tungsten Lamp	3350
Photoflood or Reflector Flood Lamp	3400
Daylight Blue Photoflood Lamp	4800
White Flame Carbon Arc Lamp	5000
High-Intensity Sun Arc Lamp	5500
Xenon Arc Lamp	6420
Daylight
Sunlight: Sunrise or Sunset	2000
Sunlight: One Hour After Sunrise	3500
Sunlight: Early Morning	4300
Sunlight: Late Afternoon	4300
Average Summer Sunlight at Noon (Washington, D.C.)	5400
Direct Mid-Summer Sunlight	5800
Overcast Sky	6000
Average Summer Sunlight (plus blue skylight)	6500
Light Summer Shade	7100
Average Summer Shade	8000
Summer Skylight Will Vary from	9500 to 30000

NOTE: Sunlight is the light of the sun only. Daylight is a combination of sunlight plus skylight. The values given are approximate because many factors affect color temperature. OUTDOORS: the sun angle, and the conditions of the sky-clouds, haze, dust particles-raise or lower the color temperature. INDOORS: lamp age (and blackening), voltage, type of reflectors and diffusers affect tungsten bulbs all of these can influence the actual color temperature of the light. Usually a change of 1 volt equals 10 degrees Kelvin. But this is true only within a limited voltage range and does not always apply to "booster voltage" operation, since certain bulbs will not exceed a certain color temperature regardless of the increase in voltage.

about Color Temperature and Light sources

**Standards of Luminous Intensity and**
**Their Color Temperatures**
Source	Color Temperature (Kelvin)
Standard British candle Hefner Harcourt pentane Acetylene Incandescentcarbon (4 watts/candle) Incandescent tungsten (1.25 watts/candle) Freezing point of platinum	1930 1880 1920 2415 2080 2400 2042

**Selected Practical Sources of Illumination and Their Color Temperatures**
Source	Color Temperature (Kelvin)	Mired Value
Sunlight (mean noon) Skylight Photographic.Daylight Crater of carbon arc (ordinary hard-cored) White-flame carbon arc Flashcube, magicube or flipflash High-intensity carbon arc (sun arc) Clear zirconium wire-filled flash Clear aluminum wire-filled flash 500-watt (photoflood) approx. 34.0 lumens/watt 500-watt (3200 K photographic) approx 27.0 lumens/watt 200-watt (general service) approx 20.0 lumens/watt 100-watt (general service) approx 17.5 lumens/watt 75-watt (general service) approx 15.4 lumens/watt 40-watt (general service) approx 11.8 lumens/watt	5400 12000 to 18000 5500 4000 5000 4950 5500 4200 3800 3400 3200 2980 2900 2820 2650	185 83 to 56 182 250 200 202 182 238 263 294 312 336 345 353 377

According to Kodak:

Mired System for light conversion

                                    1.000.000
Mired value=   -------------------------------
                          color temperature in kelvin

**`Mired Values of Color Temperatures from 2000-6900 K`**
`K`	`0`	`100`	`200`	`300`	`400`	`500`	`600`	`700`	`800`	`900`
`2000` `3000` `4000` `5000` `6000`	`500` `333` `250` `200` `167`	`476` `323` `244` `196` `164`	`455` `312` `238` `192` `161`	`435` `303` `233` `189` `159`	`417` `294` `227` `185` `156`	`400` `286` `222` `182` `154`	`385` `278` `217` `179` `152`	`370` `270` `213` `175` `149`	`357` `263` `208` `172` `147`	`345` `256` `204` `169` `145`

T₁ represent the color temperature of the original light source. represent the color temperature of the light through the filter.Using some filters, like Kodak light balancing filters, we can modify the effective color temperature. Giving to each filter a mired shift value, represented by the expression (1/T₂ - 1/T₁)*10⁶
either positive or negative, you can change the color temperature. Using yellowish filters, the mired value increases, having a positive mired shift value, resulting lower color temperature.Using bluish filters, the mired value decreases, having a negative mired sift value, resulting higher color temperature.
The above nomograph simplify to theory, showing the proper conversion filter. To find the requested filter (the mired shift value), place a straightedge on the points corresponding to the color temperature of the source, T_1,and the color temperature of the desired sourceT₂

Here are two depictions of the color temperature scale from 1000K to 10000K. They use two different mappings from CIE x,y coordinates to the surface of the RGB color cube. The first maps the "E" point, 1/3,1/3 to 1,1,1. The second maps the x,y coordinates of CIE standard illuminant C, 0.310, 0.316 to 1,1,1. The second mapping gives a more pleasing rendition as it passes through "white" at a higher temperature. Compare these with the color scales in e.g. the Cambridge Encyclopedia of Astronomy, Chapter 3.