Science popularization: About the aperture of mobile phone lens | Love playing with computers - 上海419贵族宝贝-上海后花园1314-上海品茶网-阿拉爱上海

Now the competition of smart phones is becoming more and more fierce. Many manufacturers will apply the most advanced technology to their mobile phones in order to make their products more differentiated. The lens of mobile phones is no exception. Lenovo's K900 The F1.8 super aperture lens is used for the first time. However, there are still many people who do not understand the concept of aperture, and often confuse the aperture and aperture value, thinking that F2.2 is larger than F1.8 aperture, and that F2.2 is better. Now let's have a deep understanding of aperture.

What is aperture

Aperture is a part used to control the amount of light entering the lens. The larger the aperture, the more light entering the sensor through the lens. In short, when the shutter speed is constant, the larger the aperture, the more light input, and the brighter the picture, while the smaller the aperture, the darker the picture.

In weak light, because the sensor gets less light, and the mobile phone will reduce the shutter speed and increase the iso value in order to enable the picture to get the correct exposure, so when we take pictures in dark places, it is more likely that the picture will be blurred due to hand shaking, and the picture will have more noise points due to high iso. The large aperture lens has more light entering, so when shooting in low light, the shutter speed will be relatively fast, and the iso value can also be relatively low, so that the phone can obtain better picture quality.

Aperture value

Aperture size is generally expressed by F value, F=focal length of lens/luminous diameter of lens. For example, if the maximum luminous diameter of the 50mm standard lens commonly used in digital cameras is 29.5mm, its aperture size is 50/29.5 ≈ F1.7, That is, the smaller the aperture value, the larger the aperture, This is where people often get confused.

How much larger is the aperture of F1.8 than that of F2.4?

In theory, the amount of light passing through the aperture is inversely proportional to the square of the aperture value 。 For example, the two aperture values of F2 and F2.8, F2 is 2 * 2=4, and F2.8 is 2.8 * 2.8=7.84 ≈ 8, which means that the luminous flux of F2's aperture is nearly twice that of F2.8. Now let's calculate how much more light flux of K900 with F1.8 is (2.4 * 2.4)/(1.8 * 1.8)=5.7/3.24 ≈ 1.8 than that of iPhone 4S with F2.4, that is, the light flux of F1.8 is about 1.8 times that of F2.4.

In addition, it should be noted that the aperture is not completely equal to the light flux, and the light will be lost due to internal reflection when passing through the lens.