White balance and colour temperature
In short
- Every light source has a colour; your eyes adapt to it, the camera has to be told.
- Colour temperature is measured in kelvin (K): low numbers are warm and orange, high numbers cool and blue.
- Auto white balance works well in most light; a grey card or custom setting is more reliable under tricky light.
- In RAW, white balance is just a setting you can change later without losing quality.
Light has a colour
A candle, a living-room bulb and a cloudy sky all look roughly “white” to you, because your brain quietly adjusts to the light around you. A camera sensor does not adapt. It records the light as it really is, so a room lit by bulbs comes out orange and a scene in open shade comes out blue.
White balance is the correction that tells the camera which colour should count as neutral white, so the rest of the colours fall into place.
The kelvin scale
Colour temperature comes from physics: heat an ideal dark object and it glows dull red, then orange, then white, then bluish as it gets hotter. The temperature of that glow, in kelvin, is used to describe the colour of light. The colour bar on this page shows that range, from about 800 K to 12,200 K.
Typical approximate values:
Candle flame: about 1900 K.
Household tungsten and warm-white bulbs: about 2700–3200 K.
Midday daylight: about 5200–5600 K.
Overcast sky: about 6500 K.
Open shade under a blue sky: about 7000 K or more.
These are rough guides; real light varies with time of day, weather and the particular lamp.
Why “warm” is a low number
In everyday language orange and red feel warm, blue feels cool. In physics it is the reverse: a hotter glow is bluer. So “warm” light has a low kelvin number and “cool” light a high one.
There is a second twist. The kelvin value you set on the camera describes the light you are correcting for, not the look you get. Setting 3200 K tells the camera “the light is orange”, so it adds blue. Set 3200 K in daylight and the photo turns blue; set 7500 K and it turns warm.
Auto, presets and custom
Auto (AWB): the camera guesses from the scene. It is good in daylight and mixed scenes, but can be fooled by a frame full of one colour, such as a sunset or a green lawn, and tends to leave some warmth under bulbs.
Presets: daylight, cloudy, shade, tungsten, fluorescent, flash. Each is simply a stored kelvin value (and tint). They give consistent colour across a series of shots.
Kelvin: you dial in the number directly, for example 3000 K indoors.
Custom or grey card: photograph a neutral grey or white card in the same light and tell the camera to use it as the reference. This is the most accurate option, useful for products, artwork or skin tones.
Tint and mixed light
Kelvin only covers the orange–blue axis. Some light, especially fluorescent tubes and cheap LEDs, also has a green or magenta cast. The tint setting moves the colour along that second axis.
Mixed light is harder: a window on one side and a bulb on the other cannot both be neutral at once. Usually you balance for the main light on the face and accept that the rest is warmer or cooler, or you switch off one source.
When “wrong” is right, and RAW
Correct white balance is not always the goal. A golden-hour scene “corrected” to neutral loses the warm glow that made you take the picture; the daylight or cloudy preset usually keeps it. A slightly cool setting can make snow or a blue-hour city feel colder and calmer.
If you shoot RAW, white balance is stored only as a note alongside the data. You can change it freely in editing with no loss of quality. With JPEG it is baked in; small fixes are possible, large ones damage colours. So when the light is tricky, RAW is the safe choice.