Periscope Zoom Explained: Optical vs Digital Zoom on Phones

"100x Space Zoom", "8x optical quality", "5x periscope": phone camera zoom claims are some of the most confusing numbers in tech. Some describe real lenses, some describe cropping, and some describe software guessing at detail that was never captured. This guide explains how phone zoom really works and which 2026 phones have true optical zoom.

Three kinds of zoom

Every phone zoom falls into one of three types:

1. Optical zoom uses a dedicated telephoto lens with a longer focal length. Nothing is cropped or enlarged, so you get full detail. A "5x telephoto" means a lens that magnifies five times compared with the main camera.
2. Crop zoom (often marketed as "optical quality" zoom) uses only the center of a high-resolution main sensor. A 48MP sensor cropped to the middle quarter gives a 12MP photo at 2x, with very little loss. It works well, but only at modest zoom levels.
3. Digital zoom enlarges the image beyond what any lens captured. Modern phones use AI to sharpen the result, which can look impressive on a phone screen but often invents detail. Claims such as "100x" are digital zoom.

As a rule, anything up to a camera's optical or crop zoom level will look sharp. Beyond that, quality drops quickly.

What is a periscope camera?

A telephoto lens needs a long distance between the lens and the sensor. A 5x lens would make a phone far too thick if it pointed straight out of the back.

A periscope (or folded) camera solves this by turning the light 90 degrees with a prism or mirror, then sending it sideways through the phone's body to a sensor lying flat. The long light path fits inside a thin phone, much like a submarine periscope.

Variations on the idea:

• Apple's tetraprism bounces light four times inside a prism to fit an even longer path. The iPhone 18 Pro uses it for its 4x camera.
• Samsung's ALoP design puts the lenses on top of the prism. The Galaxy S26 Ultra's 5x camera uses it, and one trade-off is that its closest focusing distance doubled from 26cm to 52cm.
• Continuous optical zoom moves lens elements inside the periscope so it can zoom smoothly across a range. The Xiaomi 17 Ultra covers 75mm to 100mm this way.

Some phones also have a regular, non-periscope telephoto for shorter zoom levels, such as the 3x camera on the Galaxy S26 Ultra and the Galaxy Z Fold 8 Ultra.

Why the main camera gives you "free" 2x zoom

Most 2026 phones have a 48MP or 50MP main camera, and some have 200MP. These sensors normally combine groups of pixels into one (called pixel binning) to produce a bright, clean 12MP photo. Zooming to 2x simply uses the full-resolution center of the sensor instead.

That is why phones without any telephoto, such as the iPhone Duo and the Galaxy Z Fold 8, can still offer good 2x photos. It is also how the iPhone 18 Pro offers 8x: it crops its 48MP 4x camera.

Sensor size, aperture and stabilization

Zoom is only one part of camera quality. Three other specs matter:

Sensor size

A bigger sensor captures more light, giving cleaner photos in low light and more natural background blur. Sensor sizes are written in a confusing old format such as 1-inch or 1/1.3-inch, and these are not real measurements: a "1-inch" sensor is actually about 13.2 x 8.8mm. All you need to know is that a smaller number after the slash means a bigger sensor (1/1.3" is bigger than 1/2.5").

Telephoto sensors are usually much smaller than main sensors. That is why zoomed photos often look worse in low light, and why the latest high-end Chinese phones with large 200MP periscope sensors lead in zoom quality.

Aperture

Aperture (written as f/1.6, f/2.8 and so on) describes how wide the lens opens. A smaller number lets in more light. The iPhone 18 Pro's main camera now has a variable aperture from f/1.48 to f/4.0, which lets it choose between more light and more depth of field.

Stabilization (OIS)

Optical image stabilization physically moves the lens or sensor to cancel hand shake. It matters most for telephoto cameras, because zoom magnifies every tiny movement.

Which 2026 phones have real optical zoom?

Popular phones with no telephoto

These phones rely on cropping the main camera for 2x and digital zoom beyond that:

• iPhone Duo, iPhone 17, iPhone Air and iPhone 17e
• Galaxy Z Fold 8 and Galaxy Z Flip 8
• Pixel 10a
• Most mid-range phones, including the Galaxy A series

The cheapest phones with a periscope camera are now in the mid-range, such as the Nothing Phone (4a) series with a 3.5x lens.

Is a bigger zoom number better?

Not always. A well-tuned 3x or 4x camera can produce better photos than a 5x camera with a tiny sensor. In DXOMARK's telephoto scores, phones with large 200MP periscope sensors (the Oppo Find X9 Ultra and vivo X300 series, around 170) led clearly, ahead of the Pixel 11 Pro XL (151), iPhone 18 Pro (143) and Galaxy S26 Ultra (141).

Two quick checks are more useful than the headline number:

• What is the telephoto's sensor size and resolution? A 48MP or 50MP telephoto with a reasonably large sensor will crop and handle low light far better than a 10MP one.
• Which zoom levels do you actually use? For portraits, 2x to 4x matters most. For concerts, sports and wildlife, 5x and beyond matters.

Teleconverters: clip-on zoom lenses

A few brands now sell clip-on lenses that extend the built-in telephoto:

• vivo's Zeiss 2.35x extender turns the X300 Pro's 85mm lens into roughly 200mm.
• Oppo's Hasselblad kit for the Find X9 Pro reaches about 230mm.
• Xiaomi's Photography Kit Pro costs A$349 in Australia.

These accessories are mostly sold in Asia and Europe, and none of these brands sell phones officially in the US or Canada.

Buying advice

• You mostly shoot people, food and everyday scenes: a phone with a good main camera and 2x crop zoom is enough. You do not need a telephoto.
• You shoot portraits or want a little more reach: look for a 3x to 4x optical telephoto.
• You shoot concerts, sports, wildlife or travel landmarks: look for a 5x periscope with a 48MP or 50MP sensor.
• Ignore "100x" claims. Judge zoom by the optical level and published sample photos.

Frequently asked questions