Periscope camera: how a smartphone gets 5x optical zoom and more

A periscope telephoto is a smartphone camera in which a prism or mirror turns the light 90° so it travels along the body. This lets a long lens for 3x-10x optical zoom fit inside a thin phone.

A periscope turns light along the body

In plain words

Remember a submarine periscope? Light comes in at the top, bounces off a mirror and travels down a tube to your eyes. A periscope camera is the same, only it "lies" inside the phone. Strong zoom needs a long "tube", but the phone is thin, so the tube is laid sideways.

How it works

Light enters the camera window on the back.
A prism or mirror turns it 90° along the body.
A long lens assembly gives a long focal length - optical magnification.
The sensor stands upright at the end of this "tunnel".
Optical stabilisation is often added, because every hand tremor shows when zoomed in.

Optical zoom brings distant objects closer without losing quality

Where you'll see it

In flagship and many upper-mid-range smartphones: "5x periscope", "3.5x periscope telephoto". You can see it as a rectangular window in the camera module. In our smartphone comparisons it appears in the camera row.

Does it matter when buying

If you photograph concerts, animals, architecture or portraits from a distance, yes - optical zoom is dramatically better than digital. For selfies and landscapes it is not critical. Look at the zoom factor and the telephoto sensor size: a periscope with a big sensor also shoots well at night.

Myths

Myth: 100x zoom is optical zoom. Reality: Optical zoom is usually 3-10x; beyond that it is digital and hybrid zoom with processing.
Myth: Any third camera is a telephoto. Reality: Often the third camera is a macro lens or a depth sensor.

FAQ

How is optical zoom different from digital?

Optical zoom magnifies with lenses without losing quality; digital zoom crops and enlarges the image.

Can I shoot portraits with a periscope?

Yes, and often better than with the main camera: less facial distortion.

Why is periscope night shooting sometimes poor?

Because of a smaller sensor and a darker aperture than the main camera.