The future of mobile cameras depends on optics. How does it work, and why will the lenses become liquid soon?
At presentations of new smartphones, cameras are praised for a long time. We are told about 50-100 megapixel sensors, magical night mode and stunning portraits. But optics are given unfairly little time. Technology is just as mesmerizing, though: liquid lenses, mirror lenses, and other innovations that will shape the future of mobile cameras are already here. Or will be on the market soon. We eliminate this gap and talk about the complex in simple language.
We will not go into the theory of the digital camera. All you need to know: An image is light that passes through a lens, refracts and converges at the focal point. And then it gets to the matrix and is transferred for processing. How much light reaches the matrix depends on the transmission capacity of the optics – the aperture ratio. It is referred to as “f / 1.8”, “1: 1.9” or “f2.0”. The recording may differ, the essence is the same: the lower this number, the “lighter” the optics .
Focal length – focal length. Photo: B&H Foto and Electronics Corp.
More often than not there are several lenses, you may come across the phrases “lens group” or “lens system”. There are usually 4-7 of them in smartphones. Why so many? Without going into details: the more lenses, the less distortion and artifacts will be in the final frame. But too many lenses, or their poor quality, can affect the aperture ratio. The everlasting compromise that manufacturers have to contend with.
By the way, many eminent companies specializing in the production of cameras and optics for decades (and some for centuries) have collaborated with smartphone manufacturers. For example, the German Zeiss and Leica, as well as the Swedish company Hasselblad. If you see such an inscription on the case, you should know that the best specialists in their field worked on the camera.
So, the distance from the focusing point to the camera matrix is the focal length (FR). Surely you or someone in your family has a camera with interchangeable lenses. They say: “18-55 mm”, “50 mm” and other numbers. This is the focal length. It is inversely proportional to the viewing angle, or the angle of image capture: the shorter the FR, the more objects will fit into the frame . Here’s a simple reminder:
The PA value depends on the size of the sensor and the type of optics. Usually they are considered reduced to a full-frame camera, the sensor size of which is close to the frame size of 35 mm film. Such a gold standard.
Therefore, when you see “26 mm”, “70 mm”, “135 mm” in the characteristics of a mobile camera, this means only the full format (or equivalent) FR – to make it easier to understand. But in reality, these distances are much shorter – because of the small sensors. Look at the thin body of your smartphone: what kind of 70 mm will fit here? On the strength of a couple of millimeters.
The inscription on the camera unit Huawei P40 Pro + reads: the aperture of the optics is in the range of f / 1.8-4.4; focal length – from 18 to 240 mm.
This is the first drawback of mobile cameras – you cannot insert a large sensor and many lenses. Dimensions are limited. The second drawback is that it is difficult to implement an adjustable RF. Above we mentioned the “18-55” lens, which is typical for amateur cameras like Canon and Nikon. This range means you can zoom in and out of objects in the frame with just one lens.
A whole system of actuators and movable lenses is responsible for the magic, which is easy to implement in large cameras, but still very difficult in smartphones. There were attempts, but the devices turned out to be cumbersome and awkward. Although work in this direction is underway, and we will certainly see movable lenses in smartphones.
In the meantime, manufacturers have to get rid of and install several modules: one for shooting at close range, the second for portraits, and so on. Why everyone is needed, and how far companies have advanced in the development of optical systems, now let’s figure it out.
Ultra wide-angle camera
“Ultra-wide” refers to a module that has an equivalent FD of less than 21 mm. When a large building or a group of friends doesn’t fit into the frame, you switch to ultra-wide.
Left – mountain lake Braies, right – Stelvio, the most beautiful road in the world according to Top Gear. Shot with Huawei P30 Pro.
Why isn’t it made the main module? You have to pay for a wide angle: distortions appear at the edges (the “barrel effect”), sharpness decreases, and the space in the frame seems to be compressed in the center and stretched at the edges. This is called perspective distortion. Try shooting an ultra-wide portrait at close range – you get a huge nose, small ears and tiny shoulders. Shoot a building from afar – it will seem even farther away. This is not a bad thing: some professional photographers use this technique and create masterpieces. But experience is important.
Manufacturers have more or less learned how to deal with the “barrel” effect – with the help of software processing. The camera itself “straightens” the curvatures at the edges. But at the same time, part of the information is lost, and the algorithms do not work perfectly – artifacts and new distortions may appear.
Huawei has advanced the farthest. In the Mate 40 Pro + smartphone, engineers have introduced an innovation that few people talk about: for the first time a free-form lens was installed in the “ultra-wide” lens.
This is an innovation not only among smartphones, but also in optics in general. The cross section of the lens is not a circle or an ellipse, as is customary, but a complex curvature. We will not discuss the history of anamorphic and paramorphic lenses here, this is a topic for a separate article. If interested, write in the comments.
The result is especially noticeable when shooting a group of people: the faces around the edges are not stretched, all the girls are happy
What does a freeform give? Distortions at the edges of the frame (distortion) disappear, detail and sharpness increase. Photos and videos get rid of the parasitic “barrel”. All smartphones do it programmatically, but with defects. The Mate 40 Pro + solves the problem at the root, even before the light reaches the sensor. Add f / 1.9 aperture, optical stabilization and autofocus here, and you get excellent shooting quality with all the benefits of wide optics.
And right now in Russia you can buy Mate 40 Pro
- To the store
- Wide angle camera
“Shirik” appeared first in phones and smartphones, long before “zooms” and “ultra-wide” ones. The focal length of wide-angle optics is in the range of 21-35 mm. All main cameras of smartphones are wide-angle, the most popular value of FR is 24-27 mm. It is at this distance that the camera captures a lot of detail and produces less distortion.
This is the most responsible, most versatile module. It can take a portrait, and a night photo, and smooth video. Therefore, there are always special requirements for Shirik optics. It should be super fast, at least f / 2.0 – to let in more light in the dark in a short amount of time. The high aperture also produces beautiful blur when shooting close-ups.
Shot with Huawei P40 Pro +
It uses the largest number of lenses – for a sharp, focused image without distortion. And the optical stabilization system dampens vibrations, shaking hands. Look for the abbreviation OIS in the specifications of your smartphone.
Another important element is the focusing system for sharp images. Now, basically, three types of focusing systems are used: contrast (the simplest), phase and laser (used in flagships), as well as their combinations. All of them give information about the distance to the object, and then with the help of a magnetic drive, the lenses are slightly displaced. This is how the camera aims at the subject.
But soon a new technology may appear in smartphones – liquid lenses. As early as 20 years ago, the French physicist Bruno Berge suggested using a mixture of oil and water.
Liquid lens design. Photo: Edmund Optics
When energized, the lens instantly changes shape and the camera instantly focuses. In addition, the system takes up much less space: one liquid lens instead of a group of 6-7 pieces of glass. It is also lightweight and very reliable. The glass can crack from impact, but water and oil do not care. According to rumors, the liquid lens may appear in the next flagship Huawei P50.
An even more revolutionary option is offered by Metalenz. The developers plan to replace the lens group with one flat one, consisting of nanostructures, representing millions of circles of variable diameter.
Array of camera modules equipped with Metalenz lenses. Photo: Justin Knight
Not only does such optics take up several times less space, but the structure can also be controlled, which means that the required amount of light can be captured. Sounds like science fiction, but Metalenz is already making these lenses. True, the customer is still unknown.
In smartphones, a telephoto lens is called a module with an equivalent FR> 50 mm, that is, with a two-fold optical zoom. He’s a telephoto, or zoom. The 50 – 70mm phased array camera is great for portraits where face-to-body proportions are natural. But the main purpose of the zoom, of course, is to bring distant objects closer. The “longer” the zoom, the more you can enlarge the image without losing quality.
The locomotive of zoom technologies in smartphones can rightfully be called Huawei. For the first time, the flagship Huawei P20 Pro used a 3x optical zoom, in the P30 Pro – a 5x optical zoom. And in 2020, engineers surprised with a double zoom: the Huawei P40 Pro + installed a bundle of 3x and 10x (!) Optical zooms. Just check the zoom range in the photo.
No zoom / zoom 3x / 10x. Shot with Huawei P40 Pro +.
Optical zoom means that magnification is achieved only due to the special structure of the lens group, only due to the laws of physics. Hybrid digital zoom uses computational photography: they “think out” the details of objects, or simply crop the frame. In any case, the quality drops. Optical zoom is not.
Details on the unique camera phone on the Huawei website
Achieving 10x magnification is a great success. You have probably already guessed what the main problem is. After all, the FR of this zoom is 250 mm. How did you manage to place the optics in a 9 mm thick smartphone? Look at the photo.
The solution is ingenious and elegant at the same time: the lenses and the sensor are located across the body, and the light passes to the matrix, reflected through five mirrors. At the same time, the mirrors are suspended on an optical stabilizer: even when shooting with a high magnification, it will be possible to take a sharp frame. As a result, the entire block of cameras is smaller than a matchbox in size and protrudes slightly from the smartphone. To get such a range of FRs on a camera, you would have to buy an expensive optics park and carry 3-5 kg of glass and metal with you.
Photos of insects, flowers, coins and other little things “in full growth” are the merit of macro photography. A separate module is often installed in budget and mid-price smartphones. For example, Huawei P Smart 2021.
Shot with Huawei P30 and Mate 20 Pro.
The focus, most often, is fixed at a short distance: 2.5-5 cm. Such modules usually have a high aperture ratio (f / 2-f / 2.4), which, together with a long FR, gives a gorgeous bokeh, that is, a very blurred background. The depth of field depends on these two indicators – the depth of field. If you’ve shot macro, you know how difficult it is to get your subject into focus. This is because the DOF is very narrow here.
In smartphones, you can find autofocus more expensive, it is much easier to take a macro photo with it. But, in any case, the resolution of the sensors does not exceed 2-5 megapixels, which is very small for high details. The best option is offered by the Huawei P40 Pro and Mate 40 Pro smartphones: their ultra-wide-angle cameras can focus at close range. And since there are high-quality sensors, optical stabilization, and high-aperture optics, the macro is of excellent quality.
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Mobile cameras have made great strides in the past 10 years. However, progress mainly concerned sensors and processing algorithms, stabilization systems. But the principles of the structure of the lenses remained the same, and as a result, the capabilities of the cameras rested on the dimensions of smartphones. New technologies in the field of optics should change the situation, many of them are already in use. In the future, camera modules will become more compact, and innovations available only to flagships will appear in budget devices.