stay iPhone 7 After the release, Portrait Mode on 7 Plus is probably the most discussed mode. This function is based on the dual cameras and algorithm on the 7 Plus, which uses the telephoto lens on the 7 Plus to create a photo with depth of field effect. In short, it is to distinguish the subject from the background, and then blur the background.

If you have ever used a SLR telephoto lens to take pictures of people in a park or at a wedding, you will be amazed at its effect and curious about how it works. The reasons are as follows.

1. Use a larger aperture to create an out of focus effect. The subject (character) is in focus while the background is out of focus.

2. Most of the time (but not every time) we use a telephoto lens to shoot, which improves the "sense of separation" between the subject and the background, because we can use its telephoto principle to get a "compression effect". This is why the nose of a person photographed with a telephoto lens looks normal, while it looks too large with a wide-angle lens.

3. But most of the time, photographers spend a lot of time learning how to use photographic equipment and technology to improve their shooting level.

In addition to the third point, Apple can help you with hardware and software, which are also the essence of Portrait Mode.

How does it work?

The dual cameras in 7 Plus use a depth of field map technology, which comes from the LiNX acquired by Apple. The data created can be drawn into a 3D terrain map by an image processor. There are many advantages brought by dual cameras, such as "Fusion". Apple uses wide-angle and telephoto lens to take photo data, and then synthesizes it into a perfect photo. Of course, there is "Portrait Mode". At present, 7 Plus can be used after upgrading to iOS 10.1, but it is only a beta version.

(The first time you open it, you will be prompted that this is the beta version)

When you switch to Portrait Mode, you will be prompted that this is only a beta version. When you use this mode, you cannot zoom, whether digital or optical. In this mode, the phone will use its 56mm telephoto lens to shoot, and then use the wide-angle lens to collect depth of field information, and then form a 9-layer depth of field map.

(9th floor depth of field map)

After drawing the 9-layer depth of field map, the system will select which layer is clearer and which layer is added with the blur effect. Apple said that this effect is called "disc" blur, which is customized by Apple. It is a more clearly defined and round blur effect than Gaussian blur.

When the telephoto lens detects the subject, it will use autofocus and other technologies to ensure the clarity of the subject, and then iPhone 7 The image processor inside will add a blurring effect to the background behind the main body.

In my shooting process, if the shooting subject is about 6 feet away from the background, you can get the maximum blur effect. When you move the camera, you can see the real-time blur effect in the viewfinder. The frame rate in real-time preview is about 30 FPS or less. I guess it should be 24 FPS, but it is enough for you to preview the real-time depth of field effect.

The delay in shooting is very low, about 600-650ms (officially announced), between HDR and standard photos. In order to lock your subject and blur it, Apple uses face recognition in this mode to tell the ISP which part needs to be clear and which part needs to be blurred.

(During the shooting process, there will be information to remind you how to shoot)

During the shooting process, you will always see a prompt message telling you whether the environment is bright enough or whether the camera is too close to the subject. Portrait Mode can only work normally in an environment with sufficient light. If it is in a weak light environment or a low contrast environment, it cannot work normally.

After taking photos in this mode, two photos will be saved in the album at the same time, one standard normal photo and one Portrait photo with blur effect (output format is JPEG).

Why use a telephoto lens to take Portrait photos?

First of all, this 56mm focal length lens is called a telephoto lens by Apple, but in photography terms, it is actually more like an ordinary lens. Apple calls it this way because it is more like a telephoto lens than another 28mm focal length lens on the fuselage. In any case, it is indeed the lens with the longest focal length among the mobile phones we have used.

The reason why Apple uses this telephoto lens to shoot Portrait Mode is that the wide-angle lens can process depth of field data better, and the wide-angle lens can shoot a wider picture without the "compression" of the 56mm focal length lens.

How about the quality?

It is reasonable for Apple to call it the beta version. There will be problems when dealing with leaves, grass or almost anything spliced with the main body. In many cases, it is impossible to distinguish it from the main body. If the main body is moving during shooting, it may not be able to be photographed. Like HDR, Portrait Mode requires a certain amount of time for image synthesis when shooting.

Let's see a group of samples

This is a typical Portrait photo, which is very well processed. The main body is well separated from the background. It can be seen that the trees are not as blurred as the background. This is the effect of depth gradient. The background will not be blurred all at once, but blurred according to the distance ladder. This will bring a more natural effect.

In this photo, we can see that a small part of BB's arm is not separated from the background. We hope that this problem can be solved through system update in the future.

This photo is well processed, but there are still some flaws in the arm position.

This photo should not have a blurring effect, because the subject and the background are connected, but still, the camera still adds a blurring effect to this photo, and the ISP also separates the subject and the background very well, which seems to have a good effect.

Finally, although this mode is still in the beta version and has some minor problems of one kind or another, the overall experience is fairly good. I believe that these minor problems can be repaired through system updates in the future.

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