A lower dark noise is preferred for most applications. Which is called dark noise (measured in electrons). With increasing exposure time and temperature electrons are generated in each pixel without light. The value is determined from the value where SNR is equal 1 (signal is as large as noise).Įven if the sensor is not illuminated each pixel shows a (dark) signal. It is more significant than only referring to the QE, as the AST combines QE, dark noise, and the shot noise (which is caused by the quantum nature of the photons). You should take the AST into account in very low light applications. This means, the lower the threshold, the more sensitive the camera. The absolute sensitivity threshold describes the lowest number of photons (minimum detectable irradiation) where the camera can differentiate useful image information in a picture from noise. If a pixel is over-exposed it is set to maximum DN and it does not contain useful information.Ģ) Absolute sensitivity threshold (AST) A high saturation capacity allows for longer exposure times. This difference might cause discussion if comparing imaging sensor data and camera data. The value is typically smaller than the full-well capacity. The saturation capacity actually used for the characterization of a camera is measured differently and directly from camera images. This corresponds to the maximum number of photons which would generate such electrons (saturation irradiance). Think of a pixel as a well and of the full-well capacity as the maximum number of electrons that can be stored in this well. 1) Full-well capacity and saturation capacity
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