White Balance (WB)

The term white balance in photography is about adjusting to the colour temperature of the visible light. Why is this necessary? Not only the light’s brightness varies – its structure (colour temperature, wavelength) can change depending on the source of light.

Visible light consists of electromagnetic radiation within the range of 400 to 700 nanometres. A shorter wavelength (high colour temperature) within this range causes the blue component; a wavelength between 600 to 700 nanometres causes the red component. White light consists of various wavelengths of visible light.

In photography colour temperature (indicated in kelvin) is essential for measuring the properties of light. The concept of colour temperature derives from a glowing, red-hot iron that radiates light with special characteristics depending on the temperature. This means that light with a lower colour temperature contains more longwave light.  The (standard) daylight has a colour temperature of ca. 5500 kelvin. Not only the light source but also influences such as reflective coloured surfaces or a change in light caused by the different absorption and light refraction of various materials can cause the colour temperature to vary (e.g. clear or coloured glass, water, air or other transparent; semi-transparent materials). A source of light such as the sun with the atmosphere’s changing absorption patterns can cause constantly changing lighting conditions. The reflection of colourful areas can change the light’s composition, e.g. green grass, red wall, yellow ceiling … More information about light can be found in the category “The correct lighting“.

Human vision adapts automatically to different light sources. Therefore we always perceive white objects as white regardless of the source of light. This skill is called chromatic adaption. In professional analog photography, various photographic films (daylight or artificial light films) and/or filters (conversion filters) are used in order to adapt to the different colour temperatures in changing lighting condition. Digital cameras usually automatically adapt to the conditions. The automatic white balance (setting “AWB“ stands for “Automatic White Balance“) orientates itself by the image sections that contain the same amount of red, green and blue. The camera’s electronics register these areas as grey. The white balance is tended to ensure that no unwanted colour cast (deviation in colour) occurs. It functions reliably in most lighting conditions (also depends on camera model). However, especially in mixed lighting conditions, it can be difficult to achieve correct adaption as only the colour temperature can be adapted to the light source.  If the image displays no neutral grey areas, it is hard for the automatic white balance to correct the image. As well as the automatic white balance, digital cameras provide the option to manually adjust the white balance. For this purpose there are settings for typical colour temperatures and lighting conditions (e.g. daylight, shade, cloudy, artificial light, lightning etc.). Additionally, high quality cameras offer the option of manual metering and sometimes there is the option of white balance bracketing. In the process, the camera captures several images with various white balance settings.

Tips on white balance
In difficult lighting situations it is recommendable to use the RAW format. Unfortunately, this format is only provided by higher quality cameras (especially SLR cameras). The filename extension of RAW images depends on the camera manufacturer. The RAW format registers all the information collected by the image sensor. This means that by using RAW convertion programs, white balance corrections can subsequently be made. Image formats such as JPG or TIFF can be corrected with an image editing program. Post-processing of images with an extreme colour cast can lead to even poorer results. To achieve the truest tones of colour possible (e.g. artwork reproductions, product photography), a grey card or a colour card can be effective. These cards are placed in the scene for the respective lighting settings for each individual image to give a neutral surface area for white balance or a colour reference for post-processing corrections.

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