🎯 RetinaNet & Focal Loss: Fixing Class Imbalance in Object Detection

Single stage detectors were fast but struggled with class imbalance. In 2017, researchers at Facebook AI introduced RetinaNet with a new loss function Focal Loss.

By down-weighting easy background examples… pic.twitter.com/1gQ9p8Ku7j

— Satya Mallick (@LearnOpenCV) 25 mars 2026

RetinaNet & Focal Loss: Fixing Class Imbalance in Object Detection Single stage detectors were fast but struggled with class imbalance. In 2017, researchers at Facebook AI introduced RetinaNet with a new loss function Focal Loss. By down-weighting easy background examples

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