How does the Light and shadow magic hand know if the CCD is dead?

Light Magic Hand want to know if there is no dead center of the CCD method is very simple, cover the lens cover to take a picture of all black, and then to the White Paper to take a full white photos, the two photos, known as dead-dead samples. If the CCD has dead spots, it is very easy to find in the black and white background photos. Note: When shooting dead spots, the ISO should be set to the minimum, the shutter speed should be faster than one-second seconds, so that less noise, will not affect the dead point analysis.