As one of the important indicators of mobile phones at present, the shooting effect has become a battleground for mobile phones. Apple and Samsung have been increasingly anxious to compete for the best camera phone for many years. Since the iPhone 4S adopted an 8 megapixel rear camera, Apple has been leading the field for many years. When Android reached an astonishing 20.7 million pixels, but still could not match the iPhone's "only" 8 million pixel camera in terms of imaging effect, we finally realized that it was not only pixels that affected the phone's photo quality. In addition to pixels, sensors, lens quality and software algorithms also affect the image quality. Samsung has been quietly improving its software and hardware strength in the past few years. With the launch of S6/S6 Edge and subsequent models, Samsung has finally moved back to one city in photography.
Pixel superstition
There are some historical reasons for people's misunderstanding that pixels are equal to photo quality. When the camera just appeared on mobile phones and PDAs, it was only 300000 pixels, and the image quality was really poor. With the rapid development of technology, mobile phone pixels have soared to an exaggerated 41 million pixels (Nokia 808). The author believes that there are two obvious leapfrog development, the first is from 300000 to 1.3 million pixels to 3.2-5 million pixels, which is basically a process from "nothing" to "something". Mobile phone photography has become a truly practical function, However, the photo taking effect at this time was still unsatisfactory, and portable photography was still the world of card cameras. The second leap is from 5 million to 8-13 million. The shooting effect of mobile phones has been further improved. With the iPhone as the representative, mobile phones can replace card cameras in many scenes. In these two leaps, the improvement of pixels has played a great role, so it left a false impression of high pixels=high image quality for users. For example, Sony's Z3 has a camera with 20.7 million pixels, but the actual photo quality is... Of course, we don't mean that high pixels are useless, high pixels will indeed bring better resolution More details and larger image size are clearly shown in the comparison between Note5 and iPhone 6. However, the quality of the image is not determined by a single factor, but by pixels, sensor area, lens, and post algorithm. Next, we will continue to explore the impact of other factors on the image quality.
Sensor area
As we all know, the most important part that determines the imaging quality of digital cameras and mobile phones is the photosensitive elements. There are two kinds of photosensitive elements, CCD and CMOS. Among them, CCD has better imaging quality, but the process is complex and the cost is high, and the power consumption is also higher than CMOS, so it is not suitable for use on mobile devices. Except for some early Sharp models, there are few mobile phones using CCD sensors. In yesterday's article, we have explained the relationship between sensor area and image quality in detail, please click To put it simply, the larger the area per pixel, the better the imaging effect. However, with the same number of pixels, the larger the area of a unit pixel, the larger the area and thickness of the sensor, so the larger the sensor area, the better. Therefore, major mobile phone manufacturers are looking for a suitable balance between pixels, sensor volume and image quality.
The Secret of the Camera Group
There are usually two important parameters for mobile camera aperture and wide-angle. The wide angle is inversely proportional to the focal length. The larger the wide angle, the shorter the focal length. The focal length is proportional to the lens thickness, that is, the shorter the focal length, the smaller the lens module thickness. Therefore, large wide-angle can not only bring a wider perspective and a larger shooting field, but also reduce the thickness of the lens module. However, the larger the wide-angle lens is, the more complex the optical design is. Aspheric lenses and high refractive index glass are needed to correct distortion and aberration. Therefore, the common wide-angle on mobile phones is 35-28mm, and users do not need to do too much trouble with this.
In addition to focal length, another important indicator is aperture. Similar to the lens of a camera, the smaller the aperture value, the larger the aperture. Due to the limitation of volume and hardware structure, the aperture of mobile phone lens is fixed. If other conditions are the same, the larger the aperture, the more light can reach the sensor. In low light environment, the picture with large aperture has higher brightness. At present, the aperture of mobile phones that take good photos generally reaches above F/2.4.
In addition to the better night shooting effect, the significance of large aperture is that greater light input can improve the shutter speed. For example, to take the same picture, we need a fixed amount of light input. With a large aperture lens, we can complete the shooting at a speed of 1/22 second. For a lens with a small aperture, if you want to get the same amount of light input, you need to extend the exposure time. If your hand shakes carelessly during this process, you will be sorry to spend the photo. Faster shutter speed, faster capture speed, which is really another big meaning of large aperture.
The lens of a digital camera is composed of multiple lenses, which can be divided into different lens groups according to their functions and functions. For example, one lens has 7 groups of 11 lenses. This lens has 9 lenses in total, and these 9 lenses are divided into 7 lens groups. Now the camera set of mobile phones is usually 4, 5 or 6 pieces, of which 5 pieces are usually marked as 5P and 6 pieces as 6P. Models with 5P or 6P lenses are often used by manufacturers as publicity stunts. Theoretically, because the technology used by different manufacturers and products is different, the quality of lenses cannot be judged simply by the number of lenses and lens groups.
In addition to the number of lenses, the material of lenses is also very important. The lenses are usually divided into glass and plastic. Glass has better light transmittance, optical performance and imaging quality. However, the cost of glass lens is high, and its shaping ability is not as strong as that of plastic. Therefore, in addition to high-end models or some mobile phones with photo taking as the main function, many mobile phones use plastic lens sets with relatively low cost.
However, most of the sapphire and gorilla glass lenses that businesses are promoting are just "protective glass" of the lens. The hardness of the surface material only determines the abrasion resistance of the lens, and does not improve the image quality. For example, the sapphire lens of iPhone 6 is actually only the outermost protective glass made of sapphire.
The Importance of Software Algorithms
In addition to these effects on the hardware, the optimization of the camera by the manufacturer, that is, the camera algorithm, is also very important for the image quality. Sony, as the most important mobile camera manufacturer at present, provides cameras for many mobile phone manufacturers and is widely used by many manufacturers, including Apple, Samsung, Huawei, Xiaomi, etc. However, different models with the same model of camera have very different imaging effects, which is caused by the gap between manufacturers' "soft power" in camera optimization and algorithm. As shown in the above figure, iPhone has made remarkable progress in the accuracy of color and white balance. We can see that the color of early iPhone models is obviously warm. After 4S, the color is more realistic. Let's take the iPhone shooting effects of foreign media for example to explain the differences of algorithms.
First of all, 4 had a problem with the white balance, and did not switch to the portrait style. The color was strange, but it also showed the importance of white balance for a photo. Even if a mobile phone is equipped with the best camera component, but there is a problem in your software algorithm and you can't accurately judge the white balance, then no matter how high the pixel, you can only shoot such a strange purple skin. Excluding the 4th generation proof, we can see that the overall color of the iPhone is warmer and the skin color is redder than that of the earlier models. At the same time, brightness optimization has also made continuous progress, the background is becoming brighter and brighter, and the contrast has also been improved to a certain extent.
In the contrast of sunset, we can see that the quality of the image has been significantly improved. In the samples taken by the early models, we can not see the trace of sunset in Shenzhen. Taking 4S as the dividing line, the later models have significantly improved the brightness of the water surface. The brightness of the water surface of 3GS and 4 is low, and many details are lost. On the premise that the pixels remain the same, 6 has some improvement in detail compared with 5S, which is the improvement in algorithm.
Under weak light conditions, 5S and 6 have made significant progress compared with previous generations of models, and the picture brightness has improved significantly compared with previous generations of models. The white balance of 3GS, 4 and 4S is obviously slightly different, and the picture is obviously yellow. 5S and 6 are already very accurate in this regard. In addition, in the enlarged sample, the iPhone 6 performs very well, and its noise control level has been greatly improved compared with 5S, which is also due to Apple's increasingly sophisticated algorithm.
Well, today's science popularization is over. Seeing here, do you have a clear understanding of the factors that affect the shooting effect of mobile phones. High pixels do not necessarily bring high image quality, and algorithms cannot make up for everything. Only by applying both hardware and software, and not having all the shortcomings in pixels, sensors, lenses, and post algorithm, can a perfect camera be truly made, which is why Samsung and Apple have long-term advantages in photography.
