A method, apparatus for executing the method, and computer program products for use in such an apparatus. The method includes scanning an interrogating light across multiple sites on an array package including an addressable array of multiple features of different moieties, which scanned sites include multiple array features. Signals from respective scanned sites emitted in response to the interrogating light are detected. The interrogating light power is altered for a first site on the array package during the array scan, based on location of the first site or on a determination that the emitted signal from the first site will be outside a predetermined value absent the altering (which allows for protecting a detector against expected overly bright sites), or is altered during the array scan based on the detected interrogating light power (which allows for compensating for light source drift during an array scan).