Understanding White BalanceThe 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 “what
heck happened?”. 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 it’s surrounding conditions. As humans we don’t recognize
changes in
color of light, for
most part, because our brains adjust for it.
The color of light is measured in degree’s Kelvin. This is referred to as color temperature. The lower
color temperature,
redder
light is. The higher
temperature,
bluer
light is.
Let’s look at sunlight. Throughout
day
color temperature of sunlight changes because of it’s 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. Let’s 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. Let’s look at film first.