car headlights

[Louis]

hi. does anyone happen to know what the color temperature of a car headlight is? i know that they use halogen bulbs, which tend to be around 2800K (i think), but i'm not sure if the wattage of headlights change this at all, or if i just have the number wrong completely.

[John Sprung]

They can be all over the place. Not all are halogen, some are ordinary tungsten/argon/borosilicate. CT will depend on the actual voltage they see. With a weak alternator and battery, they could be down around 2500 or even lower. Or they could be up more like 3200. Then there are those new bluish ones that could be 6 - 7k.

 

You could read them with a CT meter, or eyeball them against a known source.

 

 

 

-- J.S.

Edited April 8, 2005 by John Sprung

[Michael Morlan]

If you don't want to pony up the dough for CT meter, consider using a new DP trick -- the digital camera. Set the camera's color-temp to tungsten (or daylight) and take a shot of the headlight or the headlight reflecting off a white surface. Examine the color rendition either on the camera or on a calibrated computer monitor.

 

I hear some gaffers are using digital cameras to test and calibrate HMI's now.

 

Michael

[John Pytlak RIP]

If you don't want to pony up the dough for CT meter, consider using a new DP trick -- the digital camera.  Set the camera's color-temp to tungsten (or daylight) and take a shot of the headlight or the headlight reflecting off a white surface.  Examine the color rendition either on the camera or on a calibrated computer monitor.

 

I hear some gaffers are using digital cameras to test and calibrate HMI's now.

 

Michael

<{POST_SNAPBACK}>

 

Just be sure your digital camera is set to a "fixed" color temperature, and not doing an automatic white balance. Be sure your viewing software is not "correcting" or "enhancing" the color balance automatically. Shine the lights being compared onto a gray card or Macbeth color checker.

 

Even my $350 prosumer Kodak DX-4690 digital camera could be used in this way:

 

http://www.kodak.com/eknec/PageQuerier.jht...pq-locale=en_US

 

white balance:  auto, daylight, tungsten, fluorescent

 

Here is a link to a table of the color temperature of various light sources:

 

http://www.kodak.com/US/en/motion/support/h2/temp.shtml

 

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.

[L K Keerthi Basu]

In my institution we dont even have a CT and digital cameras. We students had found a alternation for this, by using our SVHS in our TV dept. I think that we are approximate to the actual CT of the light but it is a

good referance for us. Try if possible.

 

L.K.Keerthibasu