---
title: "How Camera Sensors Work — Astrophotography"
canonical: https://stackingstarlight.com/sensor
description: "How camera sensors capture starlight: pixels and photon counting, full-well and read noise, and the analog-to-digital pipeline to ADU."
---

# How Camera Sensors Work — Astrophotography

> How camera sensors capture starlight: pixels and photon counting, full-well and read noise, and the analog-to-digital pipeline to ADU.

A sensor is a grid of light-sensitive pixels. Photons free electrons that accumulate in each pixel's well during the exposure (charge proportional to light). At readout, an amplifier and **ADC** convert each well's charge into a digital number (ADU). Limits and noise enter here: **full-well capacity** caps the brightest recordable signal, **read noise** is added every readout, **quantum efficiency** sets how many photons become electrons, and **bit depth** sets quantization fineness. This pipeline — photon → electron → voltage → ADU — is where signal and several noise sources originate.

---

Source: [https://stackingstarlight.com/sensor](https://stackingstarlight.com/sensor) · Part of [Stacking Starlight](https://stackingstarlight.com) by Michael Kalika.

LLM resources: [LLM index (llms.txt)](https://stackingstarlight.com/llms.txt) · [Complete LLM text (llms-full.txt)](https://stackingstarlight.com/llms-full.txt) · [Markdown homepage (index.md)](https://stackingstarlight.com/index.md)