When you take pictures on your smartphone, it is very important that the pictures were clear, and the focus turned out to be exactly what you need. For this purpose, the object of the picture must be in focus before you press the button “take photo”. Help technology auto focus, which have their own characteristics and have found application in modern smart phones in different price segment.
When choosing a phone with a good camera, many pay attention to the number of megapixels. However, more important and useful to look at other factors that have equally serious impact on the quality of the photos. Among them — the type AF camera of a smartphone.
Contrast autofocus
The name of this technology is directly related to the principle of its work, which is the constant reading and analyzing the image of the matrix. Doing this easy microprocessor. Its main task is to move the lens in the search area with the highest contrast. Its presence is what we used to call “getting into focus”.
The most obvious disadvantage of contrast AF is its slowness. To conclude the highest level of contrast is possible only after analyzing the entire image and return the lens back, which also takes some time.
This type of focus today is mostly used in budget smartphones such as the MOTOROLA G5S Plus, SAMSUNG Galaxy J7, MEIZU M6 Note and others.
Laser around the head
The solution to the problem was to become the laser. The latter, incidentally, is quite long been used to determine the distance. How does it function? The device emitted a thin strip of light that is reflected from various surfaces and returned. The smartphone calculates the travel time of the laser, multiplies the result by the speed of light and divides by 2. The final figure will be the distance to the object, and thus cannot focus.
It is obvious that the laser has some advantages, namely high accuracy and decent speed. But it was not without flaws. The fact that the tiny dimensions of the beam are the cause of inefficiencies at large distances or in open space.
Therefore, manufacturers now combine contrasting and laser autofocus. During the launch of camera smartphone emits a beam of light to check if there are any objects. In their absence, the device begins to use the contrast autofocus.
Laser autofocus feature mostly LG phones, but there are exceptions: the same flagship Huawei P20 Pro or Asus Zenfone 2 Laser.
Phase detection autofocus
The third type of focus is called a phase. To implement additional sensors that allow the camera to capture more data for focus adjustment.
The first and foremost advantage of phase detection autofocus is much faster contrast, it is simply a must-have for shooting moving objects. In addition, the camera can assess the movement of the object by means of the sensors, hence get the opportunity of tracking autofocus.
But there are also disadvantages. Phase detection autofocus, and contrast is also not very well cope with its tasks in dark lighting conditions. Also it requires more powerful hardware, so it is usually available in smartphones to high-end segment. Among them, the Honor 10, ASUS Zenfone 5 and ZTЕ Ahop 9 Pro.
Although the faster phase detection autofocus contrast, it is still far for this option from the laser. Some manufacturers (e.g., Apple) has been improving the technology of phase AF, which allowed to bring its speed to the laser analog. The iPhone XS iPhone XS Max, the company uses the so-called “focus pixels”: the point is that the technology uses part of the pixels as the phase sensor, so shooting on a smartphone from Apple really fast.
Dual Pixel
In smartphones Samsung has long used the Dual Pixel. What is it? Previously, the company used phase detection autofocus, now the Koreans have decided that the speed of phase AF them will not be enough.
What did they do? They are implemented in each pixel with two photodiodes. Meanwhile, in the phase autofocus photodiodes were used in each pixel, and if used, then only one by one pixel. Thus, instead of 5-10 % of the pixels used for autofocus, are now 100% pixel.
In other words, the Dual Pixel is significantly improved phase detection autofocus. So he found a use in the newest Samsung smartphones.
Obviously, at this point phase detection autofocus is the right solution for most flagships, and manufacturers we are with you constantly prove it.