When image fidelity is of high importance, seeking out cameras with a better “Grade” image sensor is required.
What defines the “Grade” of an image sensor?
ON-Semiconductors (Formerly Kodak) is one of the few sensor manufacturers that provide options in sensor grades. Camera manufacturers can typically select a Grade 1 or Grade 2 sensor for their camera designs. All image sensors have some amount of defective pixels. The number of defects determines the quality grade and the value of the image sensors. Most camera manufacturers select Grade 2 due to lower cost sacrificing image performance except a select few.
Defective pixels can either be dark, as they don’t collect any light, OR be bright (hot pixel), as they are always outputting a signal.
An example of a “Hot Pixel” is shown to the right
Defective pixels, in turn can result in incorrect processing of an image!
In most all cases, cameras are corrected at the factory prior to shipment and found in the “defect map” that is stored in the camera.
Under challenging conditions or high temperature environments, additional defective pixels may appear. These can be corrected using a custom defect map.
Defect pixel correction suppresses pixels or clusters and reconstructs the expected value by interpolating the neighboring pixels. Standard algorithms use the pixel to the left or to the right of the defect pixel for the interpolation, however more advanced algorithms can be used.
Image Sensors from ON-SEMI are graded per the number of defects within the sensor. This encompasses bright and dark pixel defects along with cluster defects.
Below is an example from the ON-Semiconductor 29MP KAI-29050 sensor defect description.
** Chart is courtesy of ON-Semiconductor KAI-29050 specification
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