Traditionally analogue CCTV-Cameras can only apply brightness controlling mechanisms and technologies to the entire video image. The technologies used to achieve this are either an Auto-Iris (by adjusting the iris opening for more or less light onto the CCD Chip) or AES (for adjustment of the light per second per video frame).
Neither Auto-Iris nor AES are able to treat any specific area of the image individually - the overall brightness is calculated on the average sum of all dark and bright sections in view. This is where Wide Dynamic Range comes in. Analogue Security Cameras with WDR Function are now able to treat different areas in the image individually and apply separate brightness modifications within the same view.
Wide Dynamic Range Applications
Not every camera in a CCTV System needs to incorporate WDR functionality. Applications are scenarios in which stark contrasts and differences in darkness and brightness within the same image view can be expected. A typical scenario:
- Exit/Entry Doors: A camera is focussing in visitors entering the building through glass doors. The background outdoor scene is very bright and the camera uses AES or an Auto-Iris to tune the overall image brightness down. This results in the display of too dark faces of the entering visitors and facial details are lost. The CCTV Installer activates the Wide Dynamic Range function => The outdoor area brightness is tuned down without affecting the image area displaying the customer