Before the iPhone 12 series was released, one of the expectations people had for it was that telephoto shooting could make significant progress. We can often see renderings similar to the image below, one of the four cameras should be an ultra-telephoto lens.
▲ iPhone 12 Pro rendering. Picture from: Phone Arena
However, Apple still insisted on its idea and gave the position of the fourth camera to LiDAR lidar. The only comfort for telephoto fans is that the telephoto lens of the iPhone 12 Pro Max has been changed from 52mm to 65mm, which means that it can shoot farther and has a stronger sense of compression.
▲ iPhone 12 Pro series
Today, when Android phones have 5x and 10x optical zooms, the iPhone only supports up to 2.5x (from the main camera wide angle) optical zoom, which seems to be out of keeping up with the "trend".
So after the release of the iPhone 12 series, there were a lot of complaints on the Internet, openly or implicitly sarcasm about Apple's lack of ultra-telephoto lenses.
▲ Picture from: DXOMARK Chinese Weibo
However, DigiTimes recently quoted relevant people in the South Korean industry as saying that Apple is looking for periscope camera technology and patents in order to strengthen the optical zoom function of the iPhone, and is discussing cooperation with related companies , which has attracted the attention of the industry.
The past and present of the periscope lens
The ultra-telephoto solution Apple is looking for is the "periscope lens."
You should be familiar with this word. This kind of lens is almost standard on Android flagship phones in the past two years. So what is the principle of the periscope lens? What are the advantages?
Before getting to know this kind of lens, let's look back to 1834. At that time, the Russians built the world's first submarine "Hildra" equipped with a periscope. Twenty years later, Frenchman Marie David designed an original periscope composed of two mirrors.
▲The tall and thin tube erected above the submarine is the periscope. Image from: Pixabay
This type of periscope relies on two reflectors to make the light path folded. Therefore, soldiers can observe the enemy situation in the submarine using periscopes that extend out of the sea.
▲ Principle of periscope. Picture from: wikipedia
After learning about the periscope, let's think back to the "Long Guns and Cannons" commonly used by "Old Masters" when shooting birds and other wild animals.
▲ Lotus—the last dignity of the "old masters". Picture from: sybiji
This type of lens is called a telephoto or super telephoto lens, and the focal length can reach 200mm, 400mm, or even 800mm or more. The longer the focal length, the farther you can shoot. But you can also find that this kind of lens is generally very long.
This is because if you want to shoot farther, the lens needs to be designed to keep the optical center as far away from the photosensitive element as possible to obtain a smaller refraction angle. As the viewing angle becomes smaller, the narrower and farther the picture is captured.
▲ Moving forward and backward is the optical center.
If you don’t understand, you can raise your hand and pinch your thumb and index finger to form a round hole. Then move back and forth in the direction of the line of sight of one eye, and you will find that when you are close to the eye, you see more pictures; when you are far from the eye, you see less pictures.
Therefore, the longer the focal length, the more space is needed inside the lens, so that the optical center and the photosensitive element are kept far enough away.
▲ The lens group spacing of the Canon ultra-telephoto lens is very large. Picture from: wikiwand
But this design idea only applies to cameras. For mobile phones, if you use this design idea to make an ultra-telephoto lens, you may see a mobile phone with extremely severe lens protrusion.
So is there any good way to stuff the ultra-telephoto lens into a thin mobile phone? The periscope mentioned above is a wonderful solution.
With the help of a mirror or prism, the originally straight light path is bent abruptly to achieve more efficient refraction within a controllable thickness. This is the principle of a periscope lens.
Like a mobile phone with a 5x optical zoom, basically two mirrors or a prism are placed in the periscope lens. If the number of mirrors is increased, the optical path can achieve higher refraction, and it can achieve up to 10x optical zoom.
For example, the Huawei P40 Pro+ that supports 10x optical zoom has multiple mirrors inside the periscope lens, and the optical path is folded 5 times after entering the lens. The official website claims that the original optical path length has been extended to 1.78 times, which has achieved the wait Effective 240mm ultra-telephoto shooting.
The advantages of the periscope lens are obvious, the refractive index of the optical path is high, and the longer focal length shooting effect can be achieved under the same volume. This is the solution Apple is looking for.
Guo Mingchi said that Semco, the best lens supplier in Korea and Sunny Optical, the best lens supplier in China, will enter the Apple lens supply chain in the second half of 2020 and 2021, respectively. This may mean that we can experience 5x optical zoom (from the wide-angle focal length of the main camera) as soon as possible on the new iPhone next year.
The "telephoto battle" of mobile phone manufacturers
In the era of feature phones, we have already seen the trend of mobile phones chasing cameras.
In 2004, Sharp launched the V602SH mobile phone, which was the first mobile phone to support 2x optical zoom. However, it looks like a handheld DV, which means "buy a camera and get a mobile phone."
▲ Sharp V602SH. Picture from: ERING
After that, Nokia, Sony Ericsson, Samsung and other brands have all launched mobile phones that support multiple zoom. These phones have one thing in common, that is, the lens module is huge. Covering the brand logo and looking at the back, it is hard to believe that it is a mobile phone and not a consumer camera.
▲ Samsung Galaxy S4 Zoom
Until 2015, ASUS launched the Zenfone Zoom Hawkeye mobile phone. It cooperated with the well-known Japanese optical component company HOYA and adopted a periscope lens solution to refract the light path into the phone through a prism, thus greatly reducing the thickness of the lens module. . The phone also became the thinnest optical zoom phone at that time.
Zenfone Zoom has only one lens on the rear. ASUS's idea is to place a motor and a stud in the lens module, and adjust the distance between the optical center and the sensor to achieve 1x to 3x optical zoom.
Optical zoom has a significant advantage over digital zoom. Digital zoom uses pixel cropping to achieve a smaller area of shooting, and the image quality drops very significantly. So after ASUS started the periscope lens trend, many Android manufacturers quickly followed up. But ASUS's solution is obviously not the optimal solution. After all, ASUS has worked so hard, and the thickness of the fuselage still came to 11.9mm.
This also led to the multi-camera phones we saw later. Assign the work of the optical zoom to different lenses, and fix the structure of the periscope lens to make a fixed focus lens, such as fixed to an equivalent 125mm.
In early 2019, Huawei and OPPO successively launched the P30 Pro and Reno 10x zoom versions. The former is equipped with a 125mm periscope lens that can achieve 5x optical zoom; the latter supports a periscope lens equivalent to 160mm zoom with 6x optical zoom.
▲ P30 Pro periscope lens schematic
The release of these two models also means that the "telephoto war" of mobile phone manufacturers has officially begun. We see that more and more Android flagships are equipped with periscope lenses, Huawei P40 Pro+ and other models have even achieved 10x optical zoom with an equivalent focal length of more than 200mm.
The ultra-telephoto lens has also become an important selling point for mobile phone manufacturers. Whether it is a press conference or an official website introduction, a certain place will be reserved for it.
▲ Mi 10 Extreme Edition official website details page
But the periscope lens is not the ultimate skill of the "telephoto battle." As related technologies become more and more mature, and the cost gradually drops, periscope lenses are no longer exclusive to flagship phones. In the future, mid-to-low-end models are expected to gradually be equipped with periscope lenses.
In order to remain competitive, vivo and Xiaomi have played a "new trick" on the telephoto. For example, the concept product APEX 2020 released by vivo, the lens in its periscope lens module can be moved back and forth to achieve 80mm-120mm continuous optical zoom.
▲ APEX 2020 zoom
Does it sound familiar? The idea of the Asus Zenfone Zoom Hawkeye phone we mentioned above is exactly this. It's just that vivo successfully controlled the thickness of the phone to 8.8mm.
Xiaomi is even more "retro". It is said that it is working on a retractable lens module that can achieve "large aperture, 300% increase in light input; 20% increase in clarity."
▲ Xiaomi retractable lens solution
This solution theoretically will improve the optical effect at the telephoto end, but it can be said to be somewhat "Renaissance" in form. In addition, its waterproof and dustproof effect, volume and weight control, etc. are all doubtful.
What is the meaning of "Telephoto War"?
Looking at the current mobile phone market, it seems that there is no periscope lens, and I am embarrassed to say that I am a flagship phone.
In terms of current technology, the periscope lens is indeed the best solution for mobile phone telephoto shooting. However, we can also find that for mobile phones with periscope lenses, the lens modules are basically very prominent, suggesting to you: "I am convex, but also strong."
▲ Laser convex camera module
Should the mobile phone sacrifice the coordination and beauty of the back design in exchange for better photographic performance? This issue is not within the scope of our discussion. What we need to explore is the significance of the high-power optical zoom pursued by mobile phone manufacturers.
The current common periscope lens is generally 5x optical zoom or 10x optical zoom, which is equivalent to about 125mm or 240mm. A longer focal length means that you can shoot farther, and the 10x zoom can already capture details that are not easy to see with the naked eye.
▲ Official proofs of Mi 10 Extreme Edition
But this is only theoretical. In actual use, limited by the volume of the mobile phone, the lens module cannot occupy too much space, so the area of the photosensitive element is very limited. This makes it difficult for the image quality to reach the ideal height, especially in the dark environment, the periscope lens is basically in a state that cannot be turned on.
Take the periscope lens on Huawei Mate40 Pro as an example. When I use it when the light is complicated, slightly dark, or the contour of the subject is not clear, it is difficult to activate the optical zoom. The phone will repeatedly jump between the digital zoom of the main camera and the optical zoom of the periscope lens.
▲ In low light conditions, the Mate40 periscope lens is not easy to activate
This is not alone. The periscope lens on the mobile phone has very strict requirements for light. Even if it can be used in a low light environment, the smearing feeling of the picture is more obvious.
The reason is simple, the prism in the periscope lens will affect the amount of light entering. After the light intensity is refracted by the prism, there will be a certain attenuation. Therefore, the periscope lens has higher requirements on the sensor size than ordinary lenses. The more times the light path is refracted, the weaker the light intensity. Therefore , the optical quality of a 10x optical zoom lens on a mobile phone is generally lower than that of a 5x optical zoom lens.
There is also a common problem. The jitter that is not easily noticeable at the wide-angle end will be magnified exponentially as the focal length increases. This is a test of the anti-shake performance of the lens. At present, the 5x optical zoom periscope lens can achieve good anti-shake effect through OIS technology. However, the anti-shake performance of the periscope lens with 10x optical zoom still has much room for improvement.
▲ Shoot with Huawei P40 Pro periscope lens (5x optical zoom)
At present, it is difficult to balance the periscope lens on the issues of "good shots" and "good shots." Especially the higher the zoom factor, the more obvious this contradiction.
I have experienced the Mi 10 Extreme Edition and Huawei P40 Pro+, which are equipped with 10x (equivalent) optical zoom, which is rarely used. Friends around me also said, “I can’t think of anything that needs such a high zoom Scenes".
In my opinion, I would rather remove this lens in exchange for a larger battery with the same size and better heat dissipation. Or use material costs for better motors to get a better basic experience.
▲ Inside the Mi 10 Extreme Edition, the periscope lens occupies a lot of space
This is not to say that periscope lenses should not appear on mobile phones. I just don't think it is necessary to sacrifice too much internal space and install a lens with a focal length above 200mm that is not commonly used. The optical zoom of about 5 times may be more practical than 10 times, and it is more balanced in terms of volume and ease of use.
▲Shooting with vivo X50 Pro+ periscope lens (5x optical zoom)
5x optical zoom, converted to approximately 125mm focal length lens. It can bring a sense of perspective that is unmatched by a 2x optical zoom lens, allowing users to easily take simple and prominent images. Expect to be able to focus on this focal length when the iPhone is equipped with a periscope lens.
▲ Use Huawei Mate40 Pro periscope lens to shoot (5x optical zoom)
When mobile phone manufacturers no longer focus on "10x optical zoom" and "120x hybrid zoom", but focus on improving the image quality of 2x telephoto lens and 5x periscope lens, I think this "telephoto "War" will be back on the right track.
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