Downsampling shrinks an image or feature map to a smaller spatial resolution. It discards precise location detail, making the representation more abstract when exact positions are not important. section 1.31
A simple reduction
A 1024 × 1024 image can become 512 × 512 by averaging each group of four neighboring pixels. The result keeps broader patterns while losing fine location information. section 1.31
In a convolutional neural network, the process works in stages:
- Convolutions detect patterns, then downsampling shrinks the resulting image. section 1.31
- Repeated cycles let later convolutions detect increasingly complex patterns, from lines to object features. section 1.31
- The tradeoff is deliberate: abstraction improves content-level representation but removes precise object locations. section 1.31




