White balance (WB) is the process of removing color casts, so that objects which appear white in person are rendered white in your photo. Proper camera white balance has to take into account the “color temperature” of a light source, which refers to the relative warmth or coolness of white light. Your eye and brain will automatically adjust for color casts caused by the temperature of lights but the camera sometimes needs help.
Remember, the dress?
Due to a yellow cast in indoor lights and an incorrect exposure, the colors and shadows in the picture got muddy and confusing, creating an inaccurate photograph of the subject.
So let’s take a look at the color casts given off by different lights and why this happens.
Color temperature is a measurement of the hue of a particular light source. Have you ever noticed how the stars in the night sky are different colors? Well, this color is directly attributed to the surface temperature of the star where blue and white stars are hotter than yellow and red stars.
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is visible to the human eye and is responsible for the sense of sight.
Light gets measured in degrees Kelvin. We measure cold and heat with thermometers calibrated to show us degrees, so how come we are talking about color using the same unit of measure? Well, thanks to Lord William Thomson, the 1st Baron Kelvin (a British engineer and mathematical physicist who was directly responsible for forming the first and second laws of thermodynamics) who heated carbon, an “incandescent radiator,” and noticed that as it got hotter, the color of the carbon changed as it heated, we have a color-temperature scale. The hot-or-cold Kelvin temperature scale starts at absolute freezing 0K (-273.15ºC) while the hue-based Kelvin scale relating to color temperature starts with black as the zero point. The visible spectrum of the Kelvin scale ranges from about 1700K to 12000K or more. To the left of the visible portion of the scale is infrared. To the right is ultraviolet.
Here are some of the basic White Balance settings you’ll find on cameras:
- Auto – this is where the camera makes a best guess on a shot by shot basis. You’ll find it works in many situations but it’s worth venturing out of it for trickier lighting.
- Tungsten – this mode is usually symbolized with a little bulb and is for shooting indoors, especially under tungsten (incandescent) lighting (such as bulb lighting). It generally cools down the colors in photos.
- Fluorescent – this compensates for the ‘cool’ light of fluorescent light and will warm up your shots.
- Daylight/Sunny – not all cameras have this setting because it sets things as fairly ‘normal’ white balance settings.
- Cloudy – this setting generally warms things up a touch more than ‘daylight’ mode.
- Flash – the flash of a camera can be quite a cool light so in Flash WB mode you’ll find it warms up your shots a touch.
- Shade – the light in shade is generally cooler (bluer) than shooting in direct sunlight so this mode will warm things up a little.
White balance can be manually set matching the Kelvin temperature to a neutral (white or gray) point in the scene or on a dedicated “gray card”.
The manual method requires that you either add a gray card to the scene in a test shot or calibrate to a neutral area of the frame and then take another photo with the white balance adjusted.
Another variation is to use a stop card to calibrate the lights, shadows and colors prior to shooting.