In photography, the light illumining a scene, have an impact on colors rendition.   A white piece a paper under a tungsten bulb will look yellow.  The same white piece of paper under a fluorescent lamp will look differently.  The sensor in our cameras is recording the light reflected from a subject.  Under a colored light the scene will take a colored tint.2012-01-12-00006

The picture included in this article was shot under tungsten light.  by choosing the appropriate tungsten white balance, the color rendition closely match the scene.

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The color temperature of the light is the main element impacting the colors of a scene in normal conditions. The color temperature of light is measured in Kelvin.

Temperature Light source
1,850 K Candle light
3,000 K Tungsten bulb
4,100 K Moonlight
5,500 K Daylight, Electronic Flash
6,500 K Overcast daylight

 

You may need to correct white balance for the picture colors to be true to the subject.

How Cameras correct White Balance:

Most Cameras use Automatic White Balance.  The processor in the camera analyzes the scene and determines the proper color correction to apply when generating the .jpg image from the raw data recorded by the sensor. Recent cameras are doing a good job in determining the correct adjustment to colors.

Some Cameras allow for manual white balance adjustment.  Please consult your camera manual to know more about the different white balance settings available to you.

Should you shoot in RAW, this RAW file will contain the following information:

  • The raw data recorded by the sensor without any color correction apply by the processor of the camera;
  • A .jpg small preview of the image with color correction applied by the processor of the camera;
  • The color temperature used or determined by the processor in the camera when the scene was shot.

When you shoot in RAW you can adjust color temperature in post processing without loosing quality.  A .jpg file does not contains all the information available in a RAW file.  Adjusting white balance on a .jpg image is less efficient.

Correcting white balance in post processing

To accurately correct white balance in post-processing you will need a gray area in your scene.  Grey will equally reflect red, green and blue colors.  Your post-processing software will correct the image based on the red, green and blue luminance value.  Having a grey card with you can help when lighting is unusual.

The greatest challenge occurs when a scene is under two different sources of light.  Color temperature in Camera affects the picture in its entirety.  In post processing, some software enables you color correct only a part of the picture.  However the gradual change from one light source to another could be very difficult to fix in post-processing.

See also on Wikipedia:  Color Temperature, Color Balance and Color Cast.