Telling the Camera What is White
White Balance is a fundamental camera function that corrects for the color of light in a scene, ensuring that what appears white to the human eye also appears white to the camera. Different light sources emit light with different color ‘temperatures’—a candle flame is very orange, while an overcast sky is very blue. Our brains are incredibly good at automatically compensating for these differences, so a white piece of paper looks white to us both indoors under a lamp and outdoors in the sun. A camera sensor, however, captures the color of light literally. White Balance is the process of giving the camera a reference point so it can perform the same compensation that our brains do naturally.
The Role of Kelvin Color Temperature
White Balance is directly tied to the concept of Kelvin Color Temperature, the scale used to measure the color of light. To achieve a neutral image, the camera’s white balance setting must be matched to the Kelvin temperature of the dominant light source in the scene.
- If shooting outdoors in bright daylight (approx. 5600K), the camera’s white balance should be set to 5600K.
- If shooting indoors under tungsten lights (approx. 3200K), the camera’s white balance should be set to 3200K.
If the settings are mismatched, a color cast will result. For example, if the camera is set to 3200K but is filming in daylight, the image will look very blue because the camera is adding blue to compensate for orange light that isn’t there.
Methods for Setting White Balance
Cinematographers have several ways to set the white balance:
- Presets: Nearly all cameras have presets for common lighting conditions like ‘Daylight,’ ‘Tungsten,’ ‘Cloudy,’ or ‘Fluorescent.’
- Manual Kelvin Input: Professional cameras allow the DP to dial in a precise Kelvin value, offering the most control.
- Custom White Balance (Gray Card): This is the most accurate method. The cinematographer places a spectrally neutral white or 18% gray card in the scene’s lighting. They then point the camera at the card and use the ‘Custom White Balance’ function. This tells the camera, ‘The light hitting this neutral card should be considered pure white.’ The camera then calculates the precise color shift needed to neutralize the light source, ensuring perfect color accuracy.
White Balance and RAW Workflows
When shooting in a RAW video format, the white balance setting chosen on set does not permanently alter the image data. It is recorded as metadata, and the colorist can change it non-destructively in post-production. However, setting an accurate white balance on set is still considered crucial, as it ensures that the image seen on the on-set monitors is an accurate representation of the scene, allowing the director and DP to make confident creative decisions about lighting, costume, and production design.