Color Temperature

Before we can talk about how to control the white balance in your camera we need to know a little bit about color temperature.

Color temperature is measured in 'kelvins' formerly known as 'degrees kelvin'. To get the idea, think of a piece of metal being heated in a fire. First it gives off a reddish glow and, as it gets hotter, the color gets whiter and then, as it really warms up, it starts to give off a bluish glow. In Physics of course, we can't use any old bit of metal for the kelvin scale, we need a 'theoretical black object'. The photographer's color temperature chart is a loose interpretation of the kelvin scale, the numbers are not used in any precise manner.

As photographers all we need to know is that different types of light source emit different colors. 5000 kelvins is what we photographers call white light and is represented by 'average daylight', whatever that is, actually it's fairly obvious if you look at the chart below. We also need to know that household bulbs give off an orange light and a cloudy day will appear blue. Here's a color temperature chart covering typical light sources. In the last column I have put my recommended camera setting for each type of light. As you can see, one setting can cover several steps on the scale.

	Temp	Typical Sources	WB Setting
	1000K	Candles, oil lamps
	2000K	Very early sunrise, low effect tungsten lamps
	2500K	Household light bulbs
	3000K	Studio lights (continuous), photo floods
	4000K	Clear flashbulbs (now obsolete)
	5000K	Typical average daylight, electronic flash
	5500K	The sun at noon
	6000K	Bright sunshine with clear sky
	7000K	Slightly overcast sky
	8000K	Hazy sky
	9000K	Open shade on clear day
	10,000K	Heavily overcast sky
	11,000K	Sunless blue skies
	20,000+K	Open shade in mountains on a really clear day

When we look at objects with our eyes, we perceive white objects as white, and gray objects as gray, no matter what sort of light source we are viewing them by. This is because our brain is making the conversion for us. We 'know' that wall is white so we don't notice that it looks yellow at night (with the room lights on). If you really start to look you can see these color differences to some extent, but they are not as noticeable as they are to the camera.

Modern cameras have 'automatic white balance' so why can't we just leave it all to that? The AWB does do quite a good job but it isn't 100% accurate all the time. So sometimes we need to be able to do a few corrections ourselves. So with that in mind let's move on to talk about white balance.

Color

Introduction page.

Color Temperature

An introduction to the color temperature scale.

White Balance

How to set up your camera's manual white balance.

Gray Card

Using a gray card for color balance and exposure measurement.