Energy Received by a Digital Camera Lens: Light Energy (Photons)

The energy entering a digital camera lens is **electromagnetic radiation in the visible spectrum — light energy (photons)**.

The Imaging Chain

1. Scene emits/reflects photons (380–750 nm).
2. Lens gathers and focuses photons onto sensor.
3. Sensor (CMOS/CCD) converts photons → electron-hole pairs (photoelectric effect).
4. Analog front-end amplifies charge → voltage.
5. ADC digitizes voltage → raw digital values (RAW).
6. ISP demosaics, denoises, color-corrects → JPEG/HEIC/ProRAW.

Key Physics

• Photon energy: E = hc/λ (h=Planck, c=speed of light, λ=wavelength).
• Blue photons (~450 nm) = 2.75 eV; Red (~650 nm) = 1.91 eV.
• Silicon bandgap = 1.12 eV → detects 1100 nm and shorter (visible + near-IR).
• IR cut filter blocks >700 nm to match human vision.

Not Other Forms

• No radio waves (too long λ, low E).
• No X-rays (blocked by lens glass, would damage sensor).
• No sound (mechanical, not EM).

Light energy → electrical signal → digital image. That's the entire chain.