Dual camera in a smartphone – why, how it works and is it necessary? Dual camera in a phone - what is it, why two, three cameras on the back
In our century, photography technologies have reached unprecedented development, this also applies to mobile cameras, which traditionally have a number of significant limitations. It is clear that an increase in resolution will not lead to a noticeable improvement in quality; we have not focused only on pixels for a long time. Therefore, alternative types of shooting appear - for example, dual camera. Why do you need a dual camera in a smartphone? Let's figure it out.
What can a dual camera do?
What benefits does it provide? mobile camera? The small aperture size, small focal length and physically small matrix do not allow the smartphone to take pictures at the level of larger photographic equipment. To achieve this, smartphone manufacturers use various tricks. In 2017, a dual camera became a popular trend, and almost everyone was equipped with it. flagship smartphone, as well as a huge number of more affordable models. 
Each company uses the second camera as an auxiliary one, but everyone implements this in different ways. Each of the sensors can both capture an image and perform special tasks - for example, the second camera can have an increased focal length or more wide angle review. Due to the fact that to improve image quality and viewing angle it would be necessary to increase the size of the sensor, experts came up with the idea of using auxiliary sensor lenses in order to obtain the missing parameters. The good news is that both cameras can be used to take pictures at the same time, like eyes - the photos are processed by the processor and a common, higher-quality image is made from the two pictures. 
Previously, fashion trends were dictated by the popularity of home 3D, because the dual camera created a three-dimensional image, drawing space in pseudo-3D. And now the two-camera model is used not so much for stereo photography, but in to a greater extent to improve detail and contrast in photos and videos. This mode has a number of advantages, each of which we will examine in detail.
Dual Camera Features
What’s interesting is that dual cameras are far from an innovation - already in 2011 the first smartphones with dual cameras were presented, although then the second module c tinned exclusively to simulate augmented reality. The very first smartphone with a dual camera was invented by the companyHTC. 
There are now many applications for interacting with the camera in augmented reality mode, although now the focus is more on the optional component. Yes, in smartphones Huawei P9 and Huawei P10 the second camera shoots in monochrome mode, and the main one provides color images, and the final photo produces an ideal balance of color and quality. To this day Samsung remains the leader mobile photography, But for a long time the company did not introduce smartphones with dual cameras, later belatedly picking up the trend.Samsung Galaxy S8 and S9 Plus versions became the first devices with a dual camera from Koreans.
There are also smartphones with a dual front camera, which can be used to take advantage of selfies. However this technology Can also be used to unlock a smartphone using the owner’s face. Stands apart here iPhoneX where an advanced scanner is used FaceID which is much more complex than the IR module, since it uses a neural network component for identification. IN Apple technology The photographic part is traditionally given great attention, for example in iPhone 8 Plus the second camera is used for 2x zoom, which is achieved using optical methods without increasing the focal length or software processing.
Conclusion
Indeed, the second camera provides too many advantages to refuse such a solution. Today such giants have flagships with dual cameras asHTC, Huawei, LG, Apple, Asus, Lenovoand others. We should expect that in the near future there will be flagships with three or four, or even a large number cameras Most likely, such smartphones will look like scary insects, but here the principle of more is better, and maybe in the near future companies will come up with a way to disguise the many prying digital eyes.
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How can smartphone manufacturers surprise you? modern users? Technologies do not stand still, giving rise to new opportunities and thereby shaping fresh trends. New Dual main camera has become an increasingly popular feature on smartphones. Even last summer, there were only a few devices with this capability, but now many are well-known and Chinese companies They produce smartphones with two cameras. Let's look at the best of them.
Any normal user should wonder if Why does a smartphone need two cameras?, and isn’t this a publicity stunt by the manufacturers? The thing is that companies are gradually coming to the conclusion that cameras in smartphones are already difficult to improve: neither increasing the size of the sensor nor changing other parameters leads to significant progress in the quality of the resulting photos. The only way out is to increase the size of the camera, but then the phone will become much larger, so it is unlikely to find wide popularity among users.
The solution lay on the surface - equip the gadget with a second main camera. Since the technology is not yet widespread, manufacturers rely on an additional module different functions, but all solutions are aimed at improving photo quality. Using a dual camera, you can take pictures with different exposure parameters and, by overlaying them, get a high-quality photo. Second camera can be used for full optical zoom, and not digital, which is used in the vast majority of smartphones. With the optional camera you can change focus to finished pictures , create blurred background. On some models, the second camera creates black and white image, making the shooting process quick and the photo quality excellent.
Now let's see what interesting things it offers us modern market and take a look at best smartphones with two cameras 2017.
The smartphone is equipped 20 MP color camera and 12 MP black and white camera fromLeica. The principle of their operation is as follows: a monochrome module takes a picture, capturing as much light as possible, and thanks to the work of the color module, the resulting picture is then colored, allowing you to get a high-quality picture. The camera works clearly, autofocus works quickly, the picture turns out to be of very high quality, there are ample opportunities for manual settings shooting parameters. Front camera has a resolution of 8 megapixels. 
The remaining characteristics of the new product are also amazing. The gadget received a metal body and curved display with a diagonal of 5.5 inches and a resolution of 2560 * 1440, made using technology AMOLED. Responsible for performance 8-core processor, whose cores operate at a frequency 2.4 and 1.8 GHz. Stock RAM 4 and 6 GB V different versions, the main one is 64 and 128 GB, respectively. The gadget received a fingerprint scanner, an infrared port, 4000 mAh battery and function fast charging. Delight, not a device! Price starts from $760.
LG V20
Oukitel U20 Plus
This most cheap smartphone with two cameras, but at the same time it is of high quality and functional. It costs only $88 and proves to users around the world that dual cameras and the ability to do high quality photos– this is an opportunity not only for flagships. For a ridiculous price, you can get not just a productive device, but also a rather nice one. In its design you can notice something in common with the latest iPhones, A metal case together with 2.5D-glass makes a lasting impression.
Most affordable smartphone with two cameras received a 13-megapixel module fromSonywith interpolation up to 16 MP and an additional VGA camera. Photos receive excellent detail, and it is also possible to take photos with a blurred background. The front camera has a resolution of 5 megapixels, screen with resolutionFullHDand 5.5-inch diagonal are distinguished by the presence protective glass . Uses a 4-core processor with a frequency of 1.5 GHz, 2 GB RAM and 16 GB main memory. There is a fingerprint scanner, two SIM card slots, 4G support, battery capacity 3300 mAh. This smartphone is worth taking even for those who don’t bet prerequisite presence of a dual camera, - The model is good in all respects and perfectly balanced in terms of price and quality.
A rare new product on the smartphone market is now released without two cameras on the back side, and some have a couple of modules on the front, but today we are interested in the main dual lenses. Not every user knows what this is for and what they affect. If you have been asking yourself a similar question for a long time, but could not find the answer, then you have come to the right place. In this article we will answer the question - why do you need a dual camera in a smartphone, how to use it, and what is the point of such technology?
What is dual camera?
To begin with, I would like to clarify that a dual camera is actually one device with two sensors, and in no case a pair of separate cameras. Moreover, each of the modules has its own purpose. If the first one is completely ordinary and is responsible for the quality of shooting, then the second one is responsible for capturing the data that the main sensor could not capture, thereby improving the image. The data type may differ depending on the developer’s intention, and below we will analyze the most popular options. 
3D effect
Some dual camera phones like Honor 6X and Huawei Mate 9 the second module is necessary to create the effect of three-dimensional images. This is possible because it improves the camera's overall ability to analyze distance information from objects. Thanks to this, the user can create almost three-dimensional photographs. 
Bokeh effect
“Bokeh effect” or “ portrait mode» used in most smartphones with dual cameras. What does this effect give? It blurs background in order to visually focus attention on the main object that is in focus.
Augmented Reality
In some smartphones such as Lenovo Phab 2 Pro and Asus Zenfone AR second camera allows you to add a variety of items and objects to the image of space captured by the camera and displayed on the smartphone screen. This makes it possible, for example, to see how certain furniture will look in the house, or simply have fun watching Darth Vader walk around your room.
Detail improvements
Developers are constantly finding new tasks for the dual camera. So, in Huawei gadgets, it is necessary in order to increase the amount of detail in a photograph. The first module has a color matrix, and the second is monochrome. This combination results in sharper photographs, this applies to both color photographs and black and white. 
Shooting in Low Light Conditions
Although progress is moving very quickly, many smartphones still cannot do high quality pictures in the absence of proper lighting. In some gadgets, this problem is partially solved thanks to a dual camera. This is made possible by increasing the amount of light captured by the two sensors, which improves the quality of photographs taken at dusk or during artificial lighting. This technology is most common, again, in Huawei smartphones.
Zoom
Zooming in the form that is present in compact cameras is not yet possible to implement in smartphones, since the zoom lens is large in size and also consumes decent amounts of energy. However, limited zooming is available without it, thanks to the smartphone being equipped with a dual camera with different focal lengths of optics. Most often, the first lens has a standard viewing angle, while the second has a telescopic angle. This results in the user being able to instantly switch between two options. A striking example of such a smartphone is the iPhone 7 Plus.
In the LG G5, the developer decided to do something different - he equipped the second sensor with wide-angle optics, which allows you to capture more space in the frame. With all this, the user can also switch between shooting modes and return to the standard module if desired.
Conclusion
In this article, we talked about how a dual camera works in a smartphone and what its advantages are over a single one. Different smartphones use it differently and choose the most best option objectively impossible, since everything depends on the subjective preferences of the user. Some people care about high-quality portrait shots, while others want optical zoom, albeit a little reduced.
In conclusion, we would like to say that you should be wary of cheap models with a dual camera, since this could be a simple marketing ploy and the second module will be a sham. However, thanks to our article, you will be able to distinguish a real camera from a fake one.
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This year, the trend of increasing the number of cameras in smartphones is especially visible. Apart from the branded Google Pixel, there are no longer any significant brands whose assortment includes models only with a “regular” single camera.
And if previously only top smart phones received dual cameras, today they are already widely found in mid-range and even entry-level devices.
This year is also notable for the appearance of the Huawei P20 Pro smartphone, where not two, but three cameras have already been installed on the rear panel!
We’ll return to the three-camera Huawei later, but for now let’s talk about common dual camera modules.
What does a dual camera give?
Due to the natural parallax of two cameras placed at a certain distance, it is possible to better implement the effect of digital background blur. In many modern smartphones This mode is associated with shooting portraits.
The subject remains sharp and the background is further blurred.
Blur an object (Samsung Galaxy S9+)
Regular shot 
Applying a blur effect
The resulting image begins to resemble footage from serious system cameras, where such blur, also called bokeh, is achieved naturally due to the peculiarities of the matrix-lens combination.
Before the advent of dual cameras, this effect was also present among the functions in some smartphones, but, as mentioned above, with dual cameras the blur can be made better, although, of course, it is still not perfect.
An additional (second) camera may also have a different viewing angle.
If its viewing angle is wider than that of the main camera, then a wider shooting area will be included in the frame. This implementation option is not found very often in smartphones. As an example, we can cite LG smartphones (G5, G6, LG G7 ThinQ, V20, V30).
In LG G5 additional camera has a wider viewing angle
Choosing between the main and secondary cameras with a wide viewing angle in the LG G5 se smartphone
A more common option is when the additional camera has a narrower viewing angle. As a result, the zoom function is implemented. Typically, the equivalent focal length of the secondary camera is twice the equivalent focal length of the primary camera, resulting in a 2X zoom.
This occurs in Apple smartphones iPhone, Samsung, HTC and many others.
Additional samsung camera Galaxy S9+ has a higher equivalent focal length and provides a narrower viewing angle
Shooting with the main and secondary cameras with 2X zoom (Samsung Galaxy Note8)
Main camera 
Additional camera
But there are still situations when both cameras have the same viewing angle. This is implemented in top smartphones Huawei and Honor. A proprietary solution is used here, where the sensor of the additional camera is not color, but black and white (there are no color filters on the pixels).
According to the manufacturer, the received data from two sensors is combined in the final image, which gives a benefit in quality. In addition, it becomes possible to create “natural” black and white photographs using the matrix without color filters.
By the way, in your first and so far only smartphone with dual Sony camera Xperia XZ2 Premium, the manufacturer used a solution similar to Huawei with the same viewing angles and the use of an additional black and white camera.
Give us more! The emergence of a smartphone with three cameras
This year, Huawei has released a very interesting smartphone, the P20 Pro, in terms of photography. Its unique feature is the presence of three cameras on the rear panel!
The bottom line is that to Huawei’s traditional combination of two cameras with the same viewing angles (main and additional black and white), another camera with a narrower viewing angle was added. It is noteworthy that in in this case the equivalent focal length is not two times higher, as usual, but three times. It turns out that the zoom is already three times (3X).
Pitfalls
As a rule, additional cameras are not nearly as good as the main ones. This is also related to technical features, and with financial ones.
They are, as a rule, simpler, have a smaller sensor size, lower aperture ratio, are significantly inferior to the main ones in terms of autofocus and sensitivity, and often lack optical system stabilization, do not support a number of functions, etc.
It is not surprising that in difficult conditions (at night or when there is insufficient lighting), even if an additional camera is selected, shooting can still be carried out by the main one (this is provided by the developers).
The difference between cameras can be even more noticeable on average and primary school smartphones, where absolutely outright rubbish is installed as an additional feature.
A little history
The first smartphones with dual cameras began to appear a very long time ago.
You can remember LG Optimus 3D, released in February 2011, then appeared in March 2011, and was announced about a year later.
But the purpose of the dual cameras of the above models was completely different. At that time, 3D video (stereoscopic) was in trend, and dual cameras were needed to take stereoscopic photos and videos, which could then be viewed with a 3D effect on special screens of these smartphones.
The first attempt to use a dual camera to highlight an object in a frame with blur can be called (March 2014). But it must be said that the blur quality in the One (M8) was very poor.
In December 2014, Honor 6 Plus featured a dual camera for background blur and photo merging.
Samsung Galaxy Note8
Sony and HTC held on for a very long time (except HTC One(M8)). Accordingly, the companies released their two-chambered first-borns only in 2018.
Sony Xperia XZ2 Premium
Dual cameras are a 2016 trend in smartphones, although the first attempts are to place them on the back mobile device two photo modules, which were done much earlier. Considering that the iPhone 7 Plus is equipped with a dual camera, and others (especially the Chinese) like to imitate Apple, the tradition of equipping their offspring with a pair of cameras continues in 2017. Why does a smartphone need a dual camera? Let’s try to figure it out.
One way to use a dual camera is to take stereo photos for viewing on a 3D monitor. To do this, the smartphone is equipped with a pair of modules located on a short distance from each other. Each lens has a slightly different field of view, just as the left eye sees everything from a slightly different perspective than the right. Due to the separation of images from cameras (usually anaglyph, using red and blue filters), when using special glasses, such photos appear three-dimensional, three-dimensional.
The first smartphones with a dual 3D camera were LG Optimus 3D Max and HTC Evo 3D. However, the technology is not without its drawbacks, primarily due to the fact that the distance between lenses is different from the distance between the eyes. Smartphones with cameras that shoot in stereo have not become popular.
Expanding the field of view
The second way to use a dual module in a smartphone is to expand the field of view of the lens. Conventional (universal) optics are designed for shooting both macro and landscapes. Because of this, its viewing angle is quite limited: in order for everything to come into focus, you will have to use strongly curved lenses with a fish-eye effect, or make non-standard wide-format photosensors (for example, with 2:1 aspect ratio). Additional module, equipped with the most suitable components for landscape and panoramic photography, saves the situation.
An example of a smartphone in which the second camera is used to shoot panoramas and landscapes is the LG G5. For such gadgets, the main matrix is universal and has viewing angles of 70-90 degrees. The second is more highly specialized, with a field of view expanded to 100-120 degrees or more. This allows you to make panoramas in an instant, without gluing and moving the smartphone, which inevitably leads to graphic defects in the picture.
Shot using LG G5
Optical zoom
One of the disadvantages of smartphone cameras is the lack of optical zoom. When the subject approaches, the system simply takes a piece of the image and “stretches” it to the right size, but this does not improve the detailing. They tried to integrate a full-fledged zoom mechanism back in 2005-2006 (for example, in the Nokia N93). However, it is complicated, large (to be convinced, just look at point-and-shoot cameras with a telescopic lens) and expensive, so it is not suitable. But if you simply install two identical cameras, one of which has standard optics, and the second telescopic, then by switching between modules you can zoom in on the subject.
The dual module used for optical zoom has Apple iPhone 7Plus. Both matrices in it are the same, but one is equipped with high-aperture optics with standard parameters, and the second with a limited viewing angle, but with long-range viewing.
Optical zoom in iPhone 7 Plus
Increases photo clarity, detail and contrast
A digital camera best conveys in the picture the object on which it was focused. Side details will be rendered less efficiently. Considering that two cameras will catch more light and can focus according to different points independently, they will be able to provide a clearer transfer of details. Two photographs combined using the HDR principle combine the advantages of both cameras. For example, if one focuses on the bright summer sky, and the second on objects in the shadows, then the sky in the frame will be just as bright, and the shadowed objects will not appear in the dark.
The use of a dual camera module, one of which is color and the other monochrome (like Huawei), increases clarity and detail. A black-and-white sensor doesn't need to convey a clear hue (it just renders it as a grayscale), so it's "focused" on edges rather than color. It is for this reason that night surveillance cameras are made monochrome. A color matrix fixes colors, a black and white matrix better records small details, and together they give a bright and detailed picture.
Focus on the subject, bokeh effect
A feature of close-up lenses used in conjunction with professional cameras (mirrorless cameras, DSLRs) is the natural “bokeh effect” - blurring of the background, with extraordinary clarity of objects in focus. A universal lens (which is equipped with the matrix of an average smartphone) cannot do this in principle - optical parameters not those. But if you make two modules, one of which will focus on the subject, and the second will record what needs to be blurred, gluing frames from them will allow you to achieve the desired effect. This blur is achieved programmatically. The iPhone 7 Plus is considered the reference for shooting frames with the bokeh effect. An example of the bokeh effect with iPhone help 7Plus:
For the bokeh effect and detailing of the subject, the dual matrix is used in Xiaomi smartphones(Mi5S Plus, Redmi Pro). Not always very successful, but on average the effect is slightly better than when using purely software methods blurring the background.
Other effects
There are other purposes for which a dual camera in a smartphone can be used, but they are not so common. For example, in Xiaomi with a dual matrix you can take photos with interchangeable focus, but this feature is actually a derivative of the already mentioned sharpening function. You can also make two cameras with different fields of view, from which images will be stitched together into a seamless wide-angle panorama, but this function is also not in demand yet. In principle, you can use a double module in many ways, everything is limited only by the imagination of the developers. So in 2017 we can expect new applications.