The periscope lens
How submarine tech could mean better iPhone photos
ACCORDING TO MULTIPLE well-connected Apple leakers, the iPhone could be getting a new kind of camera in 2022; one that sees further than any existing iPhone camera without having to sacrifice any image quality.
That’s because Apple is experimenting with periscope lenses. It wouldn’t be the first to do so, either. Samsung’s Galaxy S20 and S21 Ultra both have periscopes, and other Android firms are following suit with their own high-end products. So what is a periscope lens, and why would you want it in your phone? Let’s — ahem — look into it.
WHY PERISCOPES CAN HELP YOU SEE SO MUCH FURTHER
Periscope lenses enable you to get much more powerful optical zoom without requiring an enormous lens sticking out of the back of your phone. To understand why that’s important, we need to understand how optical zooms work, and why digital zooms aren’t as good.
With optical zooms, you get the same level of detail, no matter how much you zoom in or out; with digital zoom, software tries to guess what detail a zoom lens would see. It’s clever, but no substitute for the real thing.
In order to use optical zoom, you need to change the focal length of the camera. That’s the gap between the lens or lenses and the camera sensor. Short focal lengths are brilliant for close-up photos, delivering great detail, and a very wide angle. That’s something many smartphone cameras excel at. But it’s no good for things that are far away. To shoot them, you need the focal length to be as long as possible. That means you get the same amount of detail with much longer range.
The problem with that is increasing the focal length means physically moving the lens or lenses further away from the camera sensor, and there’s not a lot of room to do that in a typically slim smartphone. Firms such as Samsung did try to solve that problem by putting enormous telescopic cameras on otherwise slim phones such as the Samsung Galaxy K Zoom, but while the results were effective enough, the phones weren’t very popular, so manufacturers decided to steal some ideas from submarines instead. Naturally.
PERISCOPES: WHY THEY’RE NOT JUST FOR SUBMARINES
We’ve all seen submarine periscopes in movies where a grizzled captain pulls down the periscope to look for the enemy. It’s a very sensible solution to a particular problem; you need to see the ships you’re targeting, but you don’t want to come to the surface. A periscope solves that problem by using angled mirrors to bounce light from the lens, which is horizontal, down the periscope tube, which is vertical.
Periscope phones do exactly the same thing, but instead of bouncing the light downwards, they bounce it sideways, moving it horizontally across the back of the phone. On the outside, the lens looks the same, but instead of sitting in front of a sensor it sits in front of a mirror. That
mirror bounces the incoming light at a right angle so it travels horizontally through other lenses until it reaches the sensor. By making the light travel that distance, you can increase the focal length far beyond what a normal smartphone camera can deliver. Where a normal camera might have a focal length of a few millimeters, periscope cameras can have a focal length measured in centimeters — without having to make the camera bump any more prominent.
THE POWER OF THE PERISCOPE
That additional focal length means much better optical zoom. How much better? In a device such as the Samsung Galaxy S21 Ultra, the periscope camera achieves 10x optical zoom. That’s something you’d normally need a proper camera for, not a smartphone. Samsung uses software to turn that into an effective 100x digital zoom, although as with all digital zooms quality degrades noticeably; as you get towards three figures, the picture becomes more impressionistic than photographic.
Like most digital zooms, the figure of 100x here is more about looking good on a spec sheet. While the Samsung is capable of shooting at up to 108 megapixels, at 100x zoom that’s 108 megapixels of jaggy and indistinct detail. However, as our friends at Techradar (techradar.com) pointed out in their Samsung review, what’s happening at 100x zoom on the Samsung is effectively the same thing that happens at 10x zoom on phones without optical zoom lenses. And if you stick to the 10x optical zoom, the results are superb, enabling you to get really close to faraway things without losing any detail.
DO YOU NEED A PERISCOPE
LENS SYSTEM IN YOUR iPHONE?
The short answer is yes; it means longer range for photography and for video too. But how much longer that range will be depends on a lot of things, not least how much room Apple can make inside the iPhone’s case for that horizontal lens assembly.
It’s clearly possible, as Samsung’s Galaxy Ultra demonstrates, but don’t hold your breath for a periscope lens in the iPhone 13 mini. For the time being, periscopes are more likely to appear in Apple’s biggest phones, most likely the iPhone 13 Pro and the iPhone 13
Pro Max.