Your phone can focus so fast | thanks to these high-tech

Last month I have written an article about the phone fill light science articles, to analyze the reasons behind the xenon flash less and less.In fact, the last two years with the overall level of mobile phone camera up, the other one had no people Pay attention to the function of the degree of concern is also followed by more and more it is the mobile phone camera focus module.


Your cell phone focus so fast thanks to these high-tech

Early in the year when people use smart phones to take pictures, I am afraid that few people will pay attention to how the camera is focusing on the simple click on the screen looking at the camera to complete their own focus and then click a photo to complete the matter.Only the last year or two, Focusing speed of the word was gradually surfaced, 0.5 seconds, 0.3 seconds, 0.1 seconds or even 0.03 seconds what the 'speed focus' all of a sudden all out, so that consumers feel confused and confused.


Today's press conference on the speed of this parameter is essential

Now I'll give you a detailed look at the current focus of several mainstream camera mode, as the focus of their time, sorry, I made it clear that I can not be measured, but I remind you here, manufacturers at the press conference or product copy on the promotion The so-called focus speed, we look like, the actual time constraints of the shooting speed of the factors too much, which we will be mentioned later.

We first talk about the relative number of the original focus - contrast focus. Contrast focus principle is based on the contrast of the focus of the screen changes, looking for the maximum contrast when the lens position, which is the exact focus position.


Contrast-Focusing (gif motion source pixinfo.com)

We take a coin, for example, the beginning of the screen is a virtual focus state, then move the lens, people can see the coins in the screen gradually clear up until a certain position (focus state) coins the most clear, but the camera model The group itself is not aware at this time has been coke is completed, the lens will continue to move, then people will see the coins and become blurred when the camera module was aware of the lens 'passing the station', so back To a clear focus of the location, so a focus on the complete.


Gif on the top of the Chinese interpretation of the dynamic map (picture from the new photography)

In fact, look at the above paragraph we can understand the contrast of the disadvantages of focusing, and yes is time-consuming too long from the beginning of the lens focus to the end of the focus has been moving to complete the 'walk through the station' after the fallback process is To increase the focus of the trip to the user's intuitive feeling is the focus slower.Also because of the contrast to detect the contrast of the screen, once the subject is close to the background color (such as in front of a white wall to take a piece of white paper) In order to achieve more difficult to focus.

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Phase Focus: The highest focus of the heat quickly

From 2015 people seem to begin to notice a PDAF unknown English frequent, it seems that any new cell phone without PDAF becomes obsolete .In fact, PDAF is more popular point called phase focus early in the early 2015 Samsung S5 It has emerged.

The principle of phase focusing is to set aside some obscuring pixels on the photosensitive element, which is used for phase detection. The focus offset can be determined by the distance between pixels and their changes.


Professional cameras usually have an independent focus sensor (picture from poco.cn)

We know that traditional SLR cameras have a focus sensor, there are vice-reflector in the back of the reflector, the sub-reflector will be part of the light incident from the lens to the focus sensor to determine the focus through the range, then the system control the lens Move the completion of auto-focus.But due to the high degree of integration of mobile phone camera module requirements, independent of the focus sensor is certainly not put in, so people directly in the CMOS (photosensitive element) to set aside pairs of pixels to mask the phase detection .


How Phase Focus Works (Picture from New Photography)

The masking pixel is composed of two pixels in pairs, and two pixels are imaged by the microlens respectively.The focusing system can judge whether the lens should move forward or backward according to the position of the judgment signal crest so as to quickly and accurately focus.


Phase contrast contrast focus, shorten the speed of travel (picture from the hummingbird network)

Focus contrast does not require repeated movement of the lens, focusing a lot of short trip, the focus clean process does not hesitate.My drawback is that the need to use the CMOS pixel on the occlusion of the phase detection, so the focus of the phase of the light intensity requirements If the ambient light intensity is too weak (such as dark light or night), the normal operation of the obscured pixels is likely to be affected, the focus accuracy and speed will be a problem.

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Laser / dual-core AF: come from behind the pros and cons

Laser focus appears in the first year there are some, but only in the last year a large area in the domestic mobile phone to see it in the figure to determine whether a mobile phone laser focus is very simple: Now you use the phone in turn, just look at To the rear of the lens next to a black opaque 'sunroof', 90% probability of your phone supports laser focus. Or open the camera interface in the dark, if the phone supports laser focus, you will see from the black ' In the red light.


The laser focus module (on the right side of the camera) is easy to see

The principle of laser focus is through the laser sensor to emit low-power laser, by calculating the laser to the subject to and from the time to determine the distance of the subject from the lens, in order to achieve more accurate and high-speed focus.

The advantage of laser focus is the use of active rangefinder method, so the whole process of focusing the environment is very small probability of interference, that is in the dark and night shot of the occasion is still able to focus more accurately.But the defect is the laser sensor emits Of the laser energy is too small, more than 0.5 meters on the attenuation of almost the same, so far away from the shooting focus is not much use.

Another term - dual-core focus is the second half of last year was a cell phone manufacturers sizzling, and this technology is not the earliest fame in the field of mobile phones, but the camera circles 2013 Canon EOS 70D released the first to use dual-core AF By the way, Canon gave the technology a long list of names: full-pixel dual-core CMOS AF.


Canon EOS 70D (released in 2013) pioneered the use of dual-core AF technology

This technology is the first show in the phone circle is released last year, Samsung S7 and S7 edge. Full pixel dual-core focus of each pixel in the distribution of the two photodiodes, PDAF (phase focus) is stronger than the ability to In the absence of pixels under the premise of the completion of the phase difference detection, and focus detection system in each pixel above the distribution, so focus accuracy and speed have improved.


Samsung S7 / S7 edge in the mobile phone industry first to use dual-core focus technology

Samsung's reputation as a manufacturer of new products, its flagship dual-core focus is not all pixels, but by custom CMOS with Sony, in this CMOS specifically set up a number of dual-core point of focus.According to its official propaganda, this The purpose of the practice is to focus on fast on the basis of ensuring high-quality output. Someone asked it and full-pixel dual-core AF who is better? I do not personally have better than concubine, can only say that even two dual-core AF Speed ​​difference, that point the gap is definitely not feel the human eye out ...


Customized production of the Sony IMX398 uses a non-full-pixel dual-core AF

We may also found that the above mentioned focus of the various types of pros and cons, but coincidentally, their strengths and weaknesses are basically complementary.So some manufacturers simply come up with a mobile phone at the same time into a variety of focusing technology Approach, that is, we say 'hybrid focus.' This method than the use of any kind of focus alone effect is better, but the cost is clearly necessary to increase, so hybrid focus is now usually only appear in each of the flagship product , The entry level is also 'no Fu consumption by'.


In view of this, the hybrid focus to become the flagship of many mobile phones

In fact, summed up the main focus of the way or three, dual-core focus itself is a sub-phase focus of the classification, but because it was stir-fried so out on the alone. If you After reading the phone camera can focus on the new way of awareness, then I reached the purpose of writing this science text. If you have anything to say, please leave a message in the following discussion, the way to this article by a Thumbs up.

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