Digital zoom: why a "100x" photo is blurry

Digital zoom enlarges an image in software: the camera crops the centre of the frame and stretches it to full size. Unlike optical zoom, it adds no detail, so quality drops. Modern phones improve it with processing and AI (hybrid zoom and "super zoom").

Digital zoom stretches the frame

In plain words

Digital zoom is like looking at a photo by stretching it with your fingers: the more you stretch, the more "squares" and blur you see. AI super zoom is like an artist painting in details that were not in the photo: it looks better, but it is partly made up.

How it works

The camera takes part of the frame from the centre of the sensor.
That part is enlarged to full size.
Pixel binning and large sensors leave room for 2x without much loss.
Merging several shots (super resolution) adds a little detail.
At high zoom levels, neural networks paint in details.

AI paints in details at high zoom

Where you'll see it

Zoom levels in the camera app: 2x, 10x, 30x, 100x. In specs: "up to 100x digital zoom", "10x hybrid". Everything beyond the optical range is digital or hybrid.

Does it matter when buying

2x digital zoom on a main camera with a big sensor is fine. But 30x-100x is for "reading a bus number", not for nice photos. If zoom matters to you, look for a phone with an optical telephoto lens.

Myths

Myth: 100x zoom lets you shoot the Moon in detail. Reality: Some of the detail in such photos is painted in by processing.
Myth: Digital zoom is the same as cropping a photo later. Reality: Almost, but the camera can use several frames for a better result.

FAQ

What is hybrid zoom?

A mix of optics, cropping and processing.

How do I get a better photo from far away?

Use an optical telephoto lens or move closer.

Should I record video with digital zoom?

Only a little - quality drops quickly.