Digital image starts as what?

• A. Digital code
• B. Analog signal
• C. Photographic film
• D. Light intensity map

Answer: (B)

Digital images begin as a representation of light that is continuous in time and space. The camera sensor converts incoming photons into an analog electrical signal whose voltage (and thus intensity) varies smoothly across the image. Only after this analog signal is sampled and quantized by an analog-to-digital converter does it become digital data that can be stored as a digital image. So the starting form is an analog signal. The other ideas—digital code is the processed final data, photographic film is not used in digital sensors, and a light intensity map is a conceptual description, not the actual sensor output—do not describe the initial form produced by the camera.