The Sony sensors (with the exception of engineering samples) are not graded, so all the Sony sensors we use are the highest and only grade commercially available. The sensor in the Atik 4000 comes in a single commercial grade and is specified as having no column defects. The KAI11002 used in the Atik 11000 comes in grade I and II types. We fit a grade II sensor as standard as we find the premium price placed on the grade I sensor is not justified when the camera is to be used for astroimaging. In short, this is because Kodak’s grading system uses a test where the sensors are run at a high frame rate and high temperature. As our cameras are cooled, these tests become an unreliable indicator of astroimaging performance. We’ve performed our own tests found no benefit in image quality from using the expensive grade I sensors over the grade II. This means we can provide you with a premium sensor at the best possible price.