The camera imager acquires the image through exposure to light. The governing parameters for this are Aperture, Shutter Speed and AGC, where AGC sets imager array sensitivity to light. The photographic camera equivalent to this is Aperture, Shutter and ISO, where ISO identifies film sensitivity. The exposure meter in a photographic camera attempts to relate an image to the 18% gray bar(mid way) of an Ansel Adams grey scale. Photographers who shoot landscape photos use a spot meter to measure the darkest part of a scene and the lightest part of the scene they want to photograph in raw format and this generates F stop range which is used to create a new camera exposure profile. This allows the camera to optimally represent the range of grey in the landscape scene.
What I am struggling with why we need a lux meter to measure incident ambient light. Why are we not interested in a spot meter reading to calculate WDR range? A lux meter measures incident light on a scene. A Spot meter measures reflected light from a scene. Not knowing how a surveillance camera actually meters the exposure, I would say that the WDR engine is probably trying to arbitrarily take an F-Stop(or two) above and an F-Stop (or two) below the 18% gray bar setting and then add these two exposures together.
Is the Aperture being controlled based on the amount of lux hitting the imager? Or is the Aperture fixed? In landscape photography a large F-Stop setting gives alot of Depth of field and a low F-Stop setting(wide open Iris) gives poor depth of field.
It looks like the CODEC is controlling the schutter speed and AGC and also the Aperture(?) to acquire a best quality image. So we should not play with those settings manually or we do not mess up the exposure algorithm.
Granted it is a video camera not a still photo camera but the science is the same. We just add frame rate.
Any photographers got surveillance acquisition figured out?