Problem – Black or white subjects

Exposure meters can usually not distinguish between brighter and darker colours, they are colour blind. The camera doesn’t recognise colourful objects that reflect light differently under the same lighting conditions.

Instead, the camera recognises different lighting conditions. Exposure metering modes are calibrated to 18% subject reflexion on average. This causes objects that reflect more light (e.g. that are a lighter colour) to be perceived as more highly lit objects by the exposure meter. This then results in an image that is too dark as the system assumed a higher level of image brightness. Photos that are captured in e.g. sunlight on fresh snow are too dark (snow appears greyish or grey/bluish). Subjects that do not have highly reflective surfaces to dominate an image will usually appear too bright (black becomes grey).

What possibilities are there to still achieve the right exposure?

Problem solution

Grey card

  • To avoid this exposure metering problem, a photographer can use a grey card. Various sizes are available. These cards have a grey surface (about the same colour grey as the back cover of a student notebook) which reflects exactly 18% of incident light. These cards are used to meter exposure in important areas of an image in terms of lighting. The metering only occurs in that section of an image. It may be necessary to work with the camera’s spot or partial metering modes or to use an external exposure meter. 

Exposure compensation

  • A more frequently used method than the grey card is the exposure compensation method. Some experience allows the photographer to estimate in advance whether or not exposure compensation is required. In addition, photographers using digital cameras have the advantage that they can subsequently check an image after capturing it. Another tool that is available is the histogram (more information concerning this in the article “Exposure compensation“). 
  • One option for exposure compensation is the Auto Exposure Bracketing. Here the camera compensates exposure for a burst of images. The extent of the compensation must be specified in advance by the photographer.
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