Decoder. plain-English AI glossary

Face Detection

● Core

Finding where faces are in an image - typically returning bounding boxes around each face.

Think of it like

Scanning a group photo and circling where each person is before you say their name.

Example

A camera app highlights everyones face with a blue box before snapping the photo. Social media software detects faces for auto-tagging. Security systems spot peoples faces in video streams.

How it actually works

Face detection is a localization task, distinct from face recognition (identifying who). Faces vary wildly in scale, pose (profile vs. frontal), lighting, occlusion (sunglasses, hair). Cascade classifiers (Haar, boosted) were fast but dated. Modern approaches: CNNs, RetinaNet, YOLOv3 fine-tuned on face data. Handles multiple faces, extreme angles, and occlusion but struggles in extreme lighting or crowds.

For product teams

Essential for photo apps, privacy (blur faces), security, and any system that needs to find and act on people.

For engineers

Datasets: WIDER Face (diverse), Pascal Face, AFW. Metrics: precision, recall, AP. Benchmarks vary by pose and lighting difficulty.

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