If you look up mobile phone camera specs on a website like GSM Arena, you might find more and more smartphones that have what’s called a periscope camera.
Simply put, a periscope camera (also referred to as a periscope zoom lens) in a smartphone refers to a mobile phone camera unit which, due to employing a prism mirror system, extends its focal length by positioning the image sensor and zooms lens array sideways.
This limits the protuberance at the back of the phone while providing greater optical zoom than usually found on a typical smartphone camera.
The first mainstream smartphone to feature a periscope zoom camera is popularly believed to be 2019’s Huawei’s P30 Pro, although Oppo unveiled this technology at the Mobile World Congress back in 2017.
However, some people believe that the smartphone periscope camera technology dates as far back as 2004 with the Sharp 902 mobile phone which had 2x optical zoom. This is pretty impressive given that the first camera phone had hit the market only a few years earlier.
What is a periscope zoom lens?
The periscope camera is sometimes called a periscope zoom lens. This is mainly because of how the smartphone camera’s zoom lens array is positioned. To better understand this, let’s look at how typical mobile camera components are arranged.
On the back of a smartphone, you’ll find the round space(s) where the camera unit is installed and fitted with a protective glass/plastic layer that protects the lens(es) and the camera unit as a whole.
When the camera captures light information to create a picture, it enters the camera straight on and goes directly through the lens array and then onto the smartphone camera sensor.
With the periscope camera, instead of having the camera’s zoom lens array lie parallel with the back of the mobile phone, the mobile camera’s zoom lens is turned sideways, perpendicular to the back of the phone. The camera’s sensor also faces the same direction, sideways facing the side of the phone instead of the back.
How does a periscope camera work?
To understand this better, think of what the word periscope is most associated with– submarines. Submarines used periscopes, which are essentially bent tubes with mirrors or prisms, to see what’s happening above the water from below the surface.
A periscope camera works similar to submarine periscopes. A mirror system is installed where the lens would have normally been. So, instead of having light enter the camera directly through the lens and then onto the camera, the periscope system takes the incoming light and reflects it 90 degrees through the lens array and onto the sensor.
Periscope zoom vs optical zoom vs digital zoom
Optical zoom relies on moving mechanical and glass elements to achieve magnification with minimal loss in picture quality. When the glass elements that make up the lens array move back and forth in relation to each other, you can capture a wide shot of the scene or a more zoomed-in shot.
With digital zoom, this is not possible because there are no moving glass elements that can magnify the image. To make up for this, the camera crops the image and enlarges it. It then uses computational photography to fill in the rest of the pixel information that is missing. However, the results aren’t as good as with optical zoom.
Periscope zoom on smartphone cameras is similar in operation to optical zoom in that it has a lens array with multiple lenses that move back and forth to zoom in and out optically. The difference is the focal length of these two systems.
The further you zoom in, the more the focal length increases. This is why telephoto lenses for DSLR cameras are so long. They can range from about 70mm to upwards of 300mm, which is very long.
For the sake of the length of this article, I will not go into detail about focal length. However, you can read about it in-depth here.
Periscope camera and phone design
If a smartphone camera were to be fitted with an optical zoom lens similar to that of a traditional camera, the phone’s camera would stick out quite a bit at the back of the phone. On today’s smartphones where thin is king, that’s not much of an option.
Remember the Samsung Galaxy K Zoom pictured above? That phone didn’t perform too well despite having 10x optical zoom, which was unheard of for a smartphone back 2014. A lot of people didn’t like the protruding camera at the back.
The sideways design of the periscope camera makes it possible to zoom in further optically without the lens sticking out too far out from the camera body. The extra space created by having a sideways lens array and sensor makes it possible to zoom in up to 5x optically and 50x when used in combination with digital zoom, as is the case with the Huawei P30 Pro’s periscope camera.
A combination of optical zoom and digital zoom is known as hybrid zoom. However, some smartphone manufacturers have their own name for this combination.
The downside of a periscope camera
The greatest disadvantage of a smartphone periscope camera comes in the form of mobile phone real estate. In other words, because the periscope camera is designed to take up space sideways inside the phone instead of sticking out from the back, it can take up a lot of space inside the phone’s body.
This means that to get more zoom magnification on the periscope camera, phone manufacturers would have to sacrifice some components and features in order to make room for it.
In the past, images taken with standard cameras equipped with periscope lenses were less than impressive because of how blurry and dark they’d come out. This has caused those who remember periscope cameras to be apprehensive about the implementation of that technology in mobile phone cameras.
However, although the technology is still very new in smartphone cameras, it seems to be pretty impressive. At least for a phone camera.
The 5x optical zoom of the Huawei P30 Pro is noticeably better in quality than the 5x digital zoom of the Apple iPhone XS and Samsung Galaxy S10+. Have a look at the comparison here.
Conclusion
Although mobile camera periscope technology is in its infancy, it seems like more and more smartphone makers are adding it to their popular flagship phones. Perhaps this means it will get better and better as the smartphone heavyweights battle it out to have the best mobile camera on the market.
A final word of advise when it comes to dealing with a zoom system of any kind is to keep your phone as steady as possible. This is because the more you zoom in, the more camera shake becomes apparent even if you have OIS enabled. This can lead to blurry photos.
There are plenty of ways to keep your phone steady like supporting it or your arms against a solid surface. However, as resistant as I was in the beginning, I’ve discovered that the best way to stabilise your phone is to use a camera support system.
The most popular is the tripod, and for several good reasons. However, there are other phone support options in various sizes that you can check out here.
This article first appeared on my other blog thesmartphonephotographer.com. Check it out!