About the ISO, aperture and shutter of mobile phones | Love playing with mobile phones - 上海419贵族宝贝-上海后花园1314-上海品茶网-阿拉爱上海

In addition to discussing the beauty of photos, we also pay attention to the EXIF information of some photos. Among them, several values are the ones we need to pay attention to most often, namely ISO, shutter and aperture 。 This article mainly talks about the relationship and mutual influence among the three.

aperture

Aperture refers to a device used to control the amount of light that passes through the lens and enters the light sensing surface in the body. It is usually in the lens. To express the aperture size, we use the f-value, which determines how much light enters the sensor through the lens. Some manufacturers will write the lens aperture parameter as "F/2.0", "F/2.4" and so on at the press conference. This value represents the aperture size. Note, however, that the larger the number, the larger the aperture. The smaller the number, the larger the aperture. For example, F/2.0>F/2.4.

We can simply say that under the same light conditions, the shutter speed is determined by the aperture of the same ISO, focus point and metering point. The larger the aperture, the faster the shutter speed will be. The faster the shutter speed is, the faster the imaging is. In the case of hand-held mobile phone shooting, the higher the shutter speed will reduce the chances of blurred images caused by shaking hands.

Here, the author uses the SLR to demonstrate the influence of aperture size on the shutter:

In the above picture, I use F/4.0 aperture, ISO is fixed at 100, and the shutter speed under normal exposure (subject to the exposure value of SLR detection) is 1/15 second.

Let's reduce the aperture. The aperture above is F/5.6, and the ISO is also fixed at 100. The shutter needs 1/10 second to get the same exposure as the above one.

However, on mobile phones, the aperture value is fixed, because the camera components are so small, it is impossible to achieve an adjustable aperture camera at present. So let's understand the impact of shutter and ISO on the image quality on the premise that the aperture is fixed.

shutter

Shutter speed is a very important parameter in mobile phone imaging. When we look at photos taken, we often see a value called "exposure time", which is actually the shutter speed. The shutter speed can affect the imaging brightness of the whole picture.

Under the same aperture size, the same light environment and ISO, the faster the shutter, the darker the image will be. The slower the shutter, the brighter the image will be. Exposure time refers to the time when light enters the sensor.

The following author also uses SLR to demonstrate such a scenario:

With the same aperture size and ISO, if the shutter speed is too fast (1/200 second in the above picture), the light entering the lens is too short, and the picture will be dark.

With the same aperture size and ISO, by slowing down the shutter speed and increasing the exposure time (the above picture is 1/15 second), you can get a normal picture.

However, on mobile phones, the camera detects insufficient light and automatically adjusts the shutter speed. Generally, the shutter speed of 1/200 second does not appear in dark environments. The most common shutter speed on mobile phones is between 1/15 second and 1/2 second. However, it should be noted that the slower the shutter speed is, the more adverse it will be in the case of holding a mobile phone, because people are not machines, and no matter how stable you think your hands are, they are actually easy to shake. At the shutter speed of 1/15 second, the probability of blurring due to hand shaking can be controlled. However, at the shutter speed of 1/2 second, except for shooting on a tripod or in a fixed place, the rest of the pictures will be destroyed due to shaking hands.

1/2 shutter speed, that is to say, the mobile phone should not have any slight jitter during your 0.5 second exposure time. For handheld devices, no one can do it without moving for 0.5 seconds. But if you shoot at a fixed position, you can get a good image. Moreover, since ISO is fixed at 100, the picture will be relatively pure, There won't be too much noise. So under the same aperture size and ISO, if you can fix the phone, the shutter speed will directly affect the brightness of the image.

ISO

ISO sensitivity actually represents the sensitivity speed of CCD or CMOS photosensitive elements, which is an indicator similar to film sensitivity. In fact, the ISO of mobile phones is achieved by adjusting the sensitivity of photosensitive elements or combining photosensitive points, that is, by improving the light sensitivity of photosensitive elements or combining several adjacent photosensitive points to achieve the purpose of improving ISO. It is worth noting that high ISO will seriously affect the image quality, especially for CMOS light-sensitive area such as mobile phones.

In the same light scene and aperture size, ISO determines the shutter speed. Improving ISO can improve the picture. For a fool shooting machine like mobile phone, low ISO will cause the mobile phone to automatically lower the shutter speed, while increasing ISO can increase the shutter speed. In order to improve the success rate of mobile phone shooting, many manufacturers will increase the ISO in the ISO automatic mode and increase the shutter speed to increase the success rate of night shooting, such as Xiaomi 2 and iPhone 5. However, some manufacturers use slow shutter speed to increase exposure, such as Nokia 920 and 808. In fact, the author believes that Nokia's approach will be better, because the image with low ISO and long exposure will be more pure and transparent. If the ISO is forced to be improved, the picture performance will be seriously damaged.

Because the settings of the SLR are different from those of the mobile phone, it is better to use the mobile phone to express the shooting effect in this example, so the author directly uses Xiaomi 2 to make a more direct comparison with the example of the impact of ISO height on image imaging:

Under the same aperture size, ISO is set at 100, and the shutter speed is 1/50 second. Moreover, the ISO is fixed at 100, and the picture is relatively clean.

At the same aperture, ISO is raised to 400, and you can see that the shutter speed has risen directly from 1/50 second of the previous one to 1/195 second.

If ISO is directly increased to 1600, the shutter speed will be directly increased to 1/877 second. In addition, we can clearly see that the forced improvement of ISO will damage the picture.

Therefore, under the condition of sufficient sunlight, it is better to fix ISO at 100, so that the imaging quality will be better. In dark environments and shooting night scenes, the ISO can be properly improved. In addition to brightening the picture, we can also know from the above examples that improving the ISO can increase the shutter speed, and also to some extent prevent hand shake from damaging the shooting effect. This kind of improvement of ISO to achieve anti shake is also called natural anti shake. The anti shake of Nokia that is achieved by floating lens module is optical anti shake.

The phone cannot adjust aperture size and shutter speed, only ISO. Now that it can be adjusted, we should make good use of:

1. If you want to shoot night scenes, your mobile phone can support a shutter speed of at least 1/2 second or slower, you should take advantage of this advantage: set the ISO to 100, and then fix your mobile phone to shoot, then you can definitely get good photos. If the shutter speed of your mobile phone is fast, you can only improve the brightness of the picture by adjusting the ISO...

2. If you want to shoot fast moving objects and can tolerate the damage of image quality, you can increase the ISO to increase the shutter speed, so that you can easily shoot fast moving objects.

3. Under the condition of sufficient daily light, it is better to set ISO at the lowest value. Low ISO imaging will be cleaner and more transparent than high ISO images. You can see the pictures of Xiaomi 2 above.

Do you want to test how slow the slowest shutter of your machine can be? It's simple. First, set your phone camera ISO to the lowest level (some are 100, some are 50, depending on the situation), then put your phone on the table, the camera is facing the table, you will see your screen is dark, very good, then press the shutter, and check the exposure time after imaging, The exposure time of the photos taken in this way is the slowest shutter speed of your machine.

Through the above content, we know the meaning of some aperture values, and then we can buy a mobile phone in the future to have a general understanding of the parameters of the mobile phone camera. Theoretically, for mobile phones, the camera aperture is large.

If you have any comments, suggestions or questions about the author's article, please leave your comments or questions below the article, and the author will reply one by one.