What is the Difference Between a Periscope and Telephoto Camera?

Cameras are indispensable to phones. Ever since the first camera phone, cameras have been so central to phones’ branding that many companies cash in solely on their devices’ abilities to capture Pixel-perfect (pun definitely intended) photographs. Over recent years, phone makers have channeled their creative energy into improving cameras and accommodating more sensors on smartphones. The evident result is the phenomenal increase in competition between brands to offer more cameras for fewer bucks. Innovation has been the key to surviving in this competitive environment, and one camera technology that has been the epitome of innovation is periscope zoom cameras. With instant 5X or 10X optical magnification, periscopic telephoto cameras facilitate quick and easy zooming into the far-off distance.

This article talks about the uses of periscope zoom cameras, their advantages and disadvantages, and the prospective future of periscope zoom cameras. But before we start with the latest trends, here’s a quick overview of what may have led to this innovation.

A brief history of telephoto smartphone cameras

Although Apple was not the first to introduce the concept of more than one camera on phones, the company should definitely be credited for popularizing the idea and inspiring others to board the bandwagon. A leader in smartphone photography for a long time, Apple introduced a telephoto camera with 2X optical zoom on the iPhone 7 Plus in 2016. Besides optical zoom, this telephoto camera was also used to capture background depth data for portrait images.

However, smartphone companies have been on this quest to bring remote objects closer for much longer. In 2013, Nokia introduced the Lumia 1020 with a 41MP camera. While this flagship Lumia didn’t support optical zoom of any sort, the enormous image from the 41MP sensor could be cropped to emulate a pseudo zoom. To this date, smartphone brands use a similar strategy to promote cameras with large megapixel counts, such as 64MP or 108MP.

Meanwhile, certain brands also experimented shortly with actual moving lens setups similar to point-and-shoot cameras. For example, Samsung launched the Galaxy S4 Zoom in 2013 with a protruding 10X optical zoom lens and xenon flash. The retracting lens and the xenon flash led to such a strong resemblance with a point-and-shoot camera that the Galaxy S4 Zoom could rightly be called a camera running on Android and supporting cellular connectivity. The Galaxy K Zoom followed it, launching in the following year.

The concept of a periscope camera on a smartphone remained quite novel until Huawei popularized it by launching the Huawei P30 Pro in March 2019. In doing so, they became the first brand to offer it commercially. The Huawei P30 Pro, as we saw in our detailed camera review of the phone, could take shots at up to 50x magnification. However, Huawei was not the first brand to experiment with this idea — it was OPPO that first showcased a periscopic camera’s optical zooming capabilities at MWC 2017. Despite the early introduction, the technology took two years to come to a realization.

A few months after the Huawei P30 Pro, OPPO introduced the OPPO Reno 10X Zoom Edition with a similar periscopic telephoto camera setup. Around the same time, Samsung began mass-producing periscopic cameras for other manufacturers to join the race.

But before we learn about the phones that come with this technology, let us take a look at how it works and what role a periscope plays in a telephoto camera module.

What is a Periscopic Zoom Camera?

As per its textbook definition, a periscope is an optical instrument that lets anyone see around an obstacle without them being visible. It traditionally includes mirrors that reflect or prisms that refract the light at right angles, allowing people to see what’s above or below their actual line of sight. Periscopes have been used in armored vehicles like tanks or submarines for several decades. The instrument itself is harmless and can also be made for some simple fun science experiments.

The application isn’t much different when it comes to smartphone cameras. As opposed to standard telephoto cameras that offer 2X or 3X optical zoom, periscopic cameras typically offer 5X or 10X zoom by using more than a single lens along with the camera sensor. A periscope’s role is to help accommodate the array of lenses without drastically increasing the smartphone’s thickness.

To understand the role of a periscope inside a camera module, visualize the smartphone in a 3D arrangement with different axes represented by X, Y, and Z coordinates. The smartphone lies with the screen flat on the YZ plane, while its thickness can be measured along the X-axis. Traditional camera sensors and the attached lenses also lie in the YZ plane, perpendicular to the Z-axis.

In the case of a periscopic setup, however, the sensor and the lenses lie on the XZ plane and intersect the Y-axis at a right angle. At the end, opposite to the camera sensor, lies a prism that changes the direction of light perpendicular to the sensor. The use of a right-angle prism is why periscope cameras have square or rectangular cutouts instead of traditional circular ones.

Light enters through the rectangular opening for a periscope camera, is refracted at a right angle, and then passes through the lenses and reaches the sensor. To ensure that the images taken with 5X or 10X magnification are sharp, periscopic telephoto cameras are equipped with autofocus support in which the lenses move forward or backward to focus on a far off object on the sensor. This is demonstrated in the following video by Samsung:

Furthermore, at 5x or higher zoom, even subtle jolts are magnified and appear like significant movements. To avoid this exaggerated shift from the intended frame, periscope cameras are built with OIS or optical stabilization — usually in the prism. This means that the prism can move freely along multiple axes responding to gravity changes and, therefore, accommodate any sudden jerky movement.

By arranging the lenses and the right-angle prism perpendicular to the camera opening, smartphone manufacturers can save a lot of space. This prevents smartphones with periscopic telephoto cameras from being ludicrously thick than they would imaginably be if the lenses were to be placed in the same plane as other cameras on the smartphone.

There is another interesting and rather common utility of periscopes we see in cameras. SLR or DSLR cameras utilize mirrors or prisms to reflect or refract the light from the camera lens to the optical viewfinder. While there is no direct relation between periscopes inside SLR cameras and periscopic telephoto cameras on smartphones, we can’t overrule the former may have been an inspiration for the new age optical zoom.

Difference Between a Periscope and Telephoto Camera

Telephoto cameras are those that allow optical zooming with or without a moving part. In contrast, a periscope camera is primarily an extension of a standard telephoto camera. Besides the difference in orientation, telephoto and periscope cameras can be distinguished by looking at the shape of the camera opening. In fact, the rectangular opening for the periscopic camera makes it easy to be identified apart from other types of cameras. Typical telephoto cameras, on the other hand, use standard circular openings and cannot be identified in just a glance.

Given the higher number of lenses used inside a periscopic telephoto setup, a telephoto camera has a longer focal length. Lastly, as we would see in the upcoming sections, neither telephoto nor periscope cameras at present support variable focal length but some modified solutions in the future might do so.

Smartphones with a Periscopic Zoom Camera

As we mentioned above, the Huawei P30 Pro was the first commercially available device equipped with a 5x periscopic zoom; the OPPO Reno 10X Zoom Edition followed soon after. Samsung’s electromechanics also kicked off the manufacturing of these periscope camera modules in summer last year, but it took a while before they could bulk up a decent number of orders.

Long after the Huawei P30 Pro was launched, Vivo’s X30 Pro (limited to China) held the baton as the “latest phone with a periscope camera” for a while but was soon replaced by the Samsung Galaxy S20 Ultra. Launched in February 2020, the Galaxy S20 Ultra also became the first smartphone to support up to 100X hybrid zoom.

Xiaomi, which arrives early to most parties, was a latecomer to this trend. Their first phone to launch with a periscopic zoom module was the Mi 10 Youth Edition. Then came Realme’s flagship killer — the Realme X3 SuperZoom — powered by a year-old Snapdragon 855. Two of the more recent additions to this tally are the latest flagship devices from Samsung and Vivo — the Samsung Galaxy Note 20 Ultra 5G and the Vivo X50 Pro, respectively.

Huawei, the brand that has been pioneering several innovations at the photography front, launched the successors to the P30 Pro nearly a month after Samsung released the Galaxy S20 Ultra. While these smartphones — Huawei P40 Pro and P40 Pro+ — predate the others mentioned in the paragraph above, Huawei’s announcement surpasses them in terms of technology and is worth an exclusive mention. While both — the Huawei P40 Pro and the P40 Pro+ — are equipped with periscopic zoom cameras, the periscope camera on the Plus variant sports 10X optical zoom while the regular Pro features 5X optical zoom. In addition to the 10X optical zoom periscope, the Huawei P40 Pro+ also features another telephoto camera fixed at 3x optical zoom.

The more recently launched Huawei Mate 40 series follows the same terminology as the P40 series. The Huawei Mate 40 Pro and the Mate 40 Pro+ feature dedicated periscope cameras with 5x and 10x optical zoom. The Mate 40 Pro+ also features a secondary telephoto camera, just like the P40 Pro+. The Porsche Design Huawei Mate 40 Pro RS follows the Mate 40 Pro+ and comes equipped with a 10x periscopic and a 3x telephoto camera.

The technology behind periscope cameras is evolving at a relatively sluggish pace than the general number game in camera resolution. Although it has enticed both — consumers and manufacturers — it is not celebrated as other technologies like superfast charging or ever-increasing display refresh rates. Smartphone brands like OPPO have been working towards ways to address the limitations of these periscope cameras.

Before we look at these limitations, let us go over the advantages that periscopic cameras offer.

Advantages of a Periscopic Zoom Camera

As we saw above, the zooming capabilities of smartphones have evolved substantially over the last decade. Periscopic zoom cameras have set a new precedent when it comes to optical zoom on a smartphone. Their most salient advantage is that they allow you to capture a distant object or scenery very much on par with a point-and-shoot camera without any lens’s actual movement. Simultaneously, the periscope’s perpendicular orientation allows smartphone manufacturers to fit the camera sensor and the set of necessary lenses within the body of the smartphone without costing them too dearly in terms of thickness.

The difference in noise on images taken at 10X magnification using the hybrid zoom on Huawei Mate 40 Pro and digital zoom on iPhone 12

Besides the longer focal length of the periscopic telephoto camera, which is ideal for capturing distant subjects, OIS ensures that images taken with periscopic optical zoom have much less image noise than digital zoom. Besides daylight, the feature is handy when it comes to photography in low light or at night.

Other than rectifying the challenges and limitations we face with digital zoom on smartphones, periscopic zoom modules on smartphones also allow users to peek into the micro world. You can use the periscopic camera to capture macro shots, even without getting too close to an object. This is especially useful if you’re passionate about capturing insects or tiny reptiles.

However, there are certain disadvantages to this camera arrangement, as we discuss below.

Disadvantages of a Periscopic Zoom camera

Although periscopic zoom cameras add the ability to zoom into objects closely much more effectively than digital zoom, they also pose certain limitations. The biggest challenge with a periscopic telephoto setup is that while it gives you the liberty to optically zoom in on far off objects or close in on a tiny object, its focal length — and thus, zooming capabilities — are fixed to a certain value. The limited space inside the lens setup prevents the lens array from moving around too much. The movement can only facilitate autofocus but not zooming in or out. Thus, it doesn’t let you zoom in or out as freely as an actually moving zoom lens attached to a point-and-shoot, DSLR, or mirrorless camera.

This means that digital zoom kicks in at magnification values other than those supported by a periscope camera despite the periscopic setup. For instance, if a smartphone supports 5X optical zoom, the periscopic camera will not come into action until you zoom to 5X zoom and instead continue to use the primary camera or another telephoto camera supports lesser magnification with digital zoom.

Now, if you want to capture something at a focal length higher than 5X — say at 10X, the smartphone switches to the periscope camera and then digitally zooms 2X, leading to a compound zoom of 10X. Smartphone companies like to refer to this as a “hybrid” zoom, a combination of optical and digital zoom.

Huawei Mate 40 Pro with a 5X periscopic camera using optical and digital zoom to reach 50X “hybrid” zoom. Image by Ben Sin/XDA

For example, a Huawei Mate 40 Pro+ uses the primary camera between 1x and 3x focal lengths, zooming digitally as one increases the magnification. At 3X zoom and beyond, the viewfinder switches over to a telephoto camera with 3X optical zoom. This camera continues to be in use until 9.9X magnification (cropping the 3X image digitally), beyond which, the phone switches to the periscope camera with 10X optical zoom. At values above 10X magnification, the phone again crops into the 10X image — thereby relying on the “hybrid” zoom. Naturally, on devices with 5X periscopic zoom camera modules, the transition happens at 5X of the focal length.

Another key disadvantage of periscope cameras is that with the increase in focal length, the field of view is narrowed, and the aperture of the camera opening is smaller than the primary camera — assuming that lenses used in both the cameras are nearly identical. With a smaller aperture, the amount of light falling on the sensor reduces, leading to a requirement for more ambient light. As a result, images taken with a periscopic camera are either dimly lit or artificially overexposed as compared to a primary camera with a much larger aperture.

As expected, with digital zoom come noise and visual artifacts in the image. This proves that while the periscopic zoom is fairly powerful, it lacks the versatility that an actually moving telephoto lens permits.

Is periscopic zoom the future for telephoto?

The concept of periscopic telephoto cameras is a progressive step ahead of digital zoom, but the limitation that we listed above testify to the necessity of a better solution. After being the first company to innovate periscope cameras, OPPO is now working on an advanced concept with variable focal length, which would allow variable optical zoom. In August 2020, OPPO revealed its concept of the “hybrid optical zoom” that utilizes a 7-element lens setup.

A schematic sketch of OPPO’s camera with hybrid optical zoom

Instead of all lenses being equidistant to each other, these lenses are divided into three groups — two out of which can move freely. This free movement should allow a variable focal length, ranging between 85mm and 135mm, as well as changing optical zoom between 3.3X and 5.2X. This can be tied to a CMOS sensor with up to 32MP resolution and 4-in-1 pixel binning support.

At the same time, Xiaomi is working on a retractable lens setup, which can either be attached on top of the primary camera or used as a discrete telephoto lens. One major benefit of this mechanism is that the lens will utilize a much larger aperture than a periscopic module, allowing more light and, consequently, better images. Xiaomi may launch a smartphone with this retractable wide aperture lens by as early as 2021.

Xiaomi’s wide-aperture retractable lens technology with physical zoom.

Even Apple is projected to move to periscope cameras on the iPhones by 2022. While there are still two more years to go before that happens, adopting periscope cameras on the iPhone might lead them to become much more mainstream than they are right now. Until then, we will continue tracking developments in the industry that let us see without leaping too far away from reality.

What do you think about periscopic zoom cameras, and what role do you foresee for them in smartphone photography over the next few years? Let us know your thoughts in the comments below!

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