Understanding White Balance
The Color of Light
Everyone has taken at least one photograph that has been way off in color. You get it back from whoever processed it, or if it is from a digital camera you load it into your computer, and your immediate response is ďwhat heck happened?Ē. Everything has a weird color cast to it, either orange, green or blue.
Light has a definite color to it depending on light source and itís surrounding conditions. As humans we donít recognize changes in color of light, for most part, because our brains adjust for it.
The color of light is measured in degreeís Kelvin. This is referred to as color temperature. The lower color temperature, redder light is. The higher temperature, bluer light is.
Letís look at sunlight. Throughout day color temperature of sunlight changes because of itís angle and surrounding atmospheric conditions. Early in morning and late in evening sunlight gets a warm golden glow to it. Photographers refer to this time as golden hour. During middle of day however light is very blue, around 5500-6500 degrees kelvin. This is color temperature of most flash units. In shade, color temperature of light is around 7500 degrees kelvin.
Artificial light on other hand is a whole different ball game. Letís take a look at incandescent light bulbs. These are every day light bulbs. On average color temperature of a light bulb is around 3200 degrees kelvin. They have a strong orange color cast. This is evident if you are outside, late in evening and look at windows of a lit up house. The light in windows will have an orange cast that is very easy to see. It used to be that florescent lights were at about 4000 degrees kelvin. This color temperature would record with a green cast on daylight balanced film. These days florescent lights can be purchased at different color temperatures.
The Recording Media and Corrective Options
Because of way light can shift color a white object may not record as white on different recording media. As far as this article is concerned, there are two types of light recording media. One is photographic film and other is a digital camera. Letís look at film first.