/kloc-which is better, a 0.0 megapixel mobile phone or a 20 megapixel Quan Huafu SLR?

There are three reasons why the imaging quality of a 20-megapixel Quan Huafu SLR or mirrorless camera is better than that of a/kloc-0.0-megapixel mobile phone:

1. The aperture of a SLR or mirrorless camera lens is larger than that of a mobile phone.

2. The sensor area of SLR or mirrorless camera is larger than that of mobile phone.

3. The resolution of SLR or mirrorless camera lens is better than that of mobile phone.

Then why is the imaging quality of the above three points better?

Actually, as far as I am concerned, most photographers understand these three points, but they don't understand the deeper reasons behind them …

When considering optical imaging, most people only consider the geometrical optics, that is, the particle part of light. But in fact, high school physics tells us that any object has wave-particle duality, and light is no exception. Because the momentum of visible light is very small, the fluctuation of visible light is actually obvious. When considering the problem of optical imaging, the fluctuation of light should also be taken into account.

As a wave, when light passes through a slit or a circular hole, it will be diffracted. Similarly, when light passes through the aperture in the lens, diffraction also occurs. From the naked eye, the diffraction phenomenon is not obvious, because the diameter of the aperture is much larger than the wavelength of visible light, but for the tiny pixels on the camera sensor, this diffraction can not be ignored. In fact, this diffraction causes the image on the sensor to be a tiny light spot instead of an infinite resolution picture, and the image is a limited resolution picture.

In the camera, when F=P/ 1.22λ (where f is the aperture coefficient = focal length/aperture diameter, p is the pixel size, λ is the wavelength of light), the imaging system is at the diffraction limit. At this time, the camera sensor can just completely sample the image formed by the lens. If the pixel size is larger than this, the details of the picture will be lost, and it is meaningless to improve the pixel size without a smaller resolution.

At present, the size of the camera sensor in mainstream mobile phones is about 1/2 inches, where 1/2 inches does not refer to the diagonal length of the sensor, but refers to the half circumference of the effective image field, or the length of the diagonal arc of the sensor. Based on this calculation, the diagonal length of the camera sensor in the mobile phone is about 8mm, that is to say, the area of the camera sensor in the mobile phone is generally around 30mm^2. The sensor size of the full-frame camera is 24mm×36mm, which is 864mm^2. The aperture coefficient of the mainstream mobile phone camera is generally around F2, and we also calculate the camera according to F2.

Then, under the aperture of F2, we can get that the average wavelength of light is 580nm, and the pixel size at the diffraction limit is 1.4μm, that is, the pixel area is1.4μ m 2, which is 864mm^2 brought into mobile phones and full-frame cameras by 30mm^2. We can get that the effective resolution of the mobile phone lens is 65438. The effective resolution of the camera lens is 400 million pixels, but in fact, the resolution of the 1 10,000-pixel mobile phone sensor is much larger than that of the mobile phone lens, and the effective resolution of the camera sensor is much smaller than that of the lens, so no matter how high the resolution of the mobile phone camera sensor is, its actual resolution can at most catch up with the level of SLR 10 years ago.

However, there are so many extra pixels in the camera sensor of the mobile phone that it is completely useless? Not really!

What needs to be mentioned here is that the image quality of a photo is not only affected by the resolution, but also related to the noise level. If the resolution is high, but there is a lot of noise, it looks like the picture quality will be very poor. The purpose of so many pixels in the mobile phone is to control the noise. Different from the understanding of ordinary photographers, the noise control method of mobile phones is completely opposite to that of cameras. In a camera, the larger the area of a single pixel of the sensor, the more charges are accumulated on the photosensitive grid, which means that the higher the signal-to-noise ratio, the less noise is generated. Therefore, the top-end 1dx camera like Canon, which sells tens of thousands, has a pixel level of 20 million. But mobile phones are the opposite. Because the single pixel size of the mobile phone camera sensor is very small and cannot be enlarged, the pixel size can only be made smaller. In this case, although there is more noise, the noise is also smaller, the whole picture is more delicate, and the overall appearance is less noise. This is also a helpless move of the mobile phone camera, but the noise control method of the mobile phone can never be compared with the camera, so even if the high pixel can control the noise,

The above determines that a full-frame camera with a larger lens and a larger sensor will definitely have better picture quality than a mobile phone.

In addition, there is the problem of resolution. The lens is not an ideal optical system, and there will be phase differences including spherical aberration, coma, astigmatism, field curvature, distortion and dispersion. If these aberrations cannot be controlled, sharpness and resolution will be reduced. Because of the large longitudinal space of camera lens, multiple groups of lenses can be inserted to correct these aberrations, which makes the imaging quality very good. However, the vertical space of the mobile phone lens is small, so it can't hold so many groups of lenses, so the aberration is relatively large, the clarity and resolution are relatively low, and the imaging quality is not as good as that of the camera!

This is why the picture quality of mobile phones can never be compared with professional SLR or single battery!