This lecture covers the principles of high energy photon detection, including the relationship between light detection and energy levels, the efficiency of photon detection, and the use of Charge-Coupled Device (CCD) detectors. It also discusses the importance of Quantum Efficiency, the impact of different types of CCD detectors on photon detection efficiency, and the role of Anti-Reflective coatings in minimizing light reflection. Additionally, it explores the concept of Signal to Noise ratio in CCD detectors and the use of CMOS and Infra-Red detectors in photon detection.