What do the characteristics of smartphone cameras say and can you trust them?

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

Lifehacker tells how to figure out tens of megapixels and different focal lengths.

At the dawn of the development of smartphones, a separate category stood out - the camera phone: in these gadgets, maximum attention was paid to the camera. Now, every flagship model of almost every brand is trying to attract attention with the most complex and interesting camera implementation. The characteristics of the devices are masked by loud words, bold slogans, huge numbers and their own names of technologies. But is it possible to subtract anything useful from them and understand whether this camera is capable of producing a decent image? Let's figure it out now.

Key features of smartphone cameras

The characteristics of a smartphone camera are essentially the same as those of any digital camera. But you need to understand what this or that parameter is responsible for.

Megapixels

Manufacturers pay the most attention to them in advertising campaigns. A pixel is a light-sensitive element on a camera sensor, or a photodiode. It consists of four subpixels, each of which, due to light filters, allows only light of its own shade to pass through. Most often these are red, blue and green. From the combination of these colors, a point of the required shade and desired brightness is obtained.

Some manufacturers are moving away from the most popular scheme and add white or yellow to the red, blue and green color filters. In this case, the photodiode captures more light and the images are brighter.

Megapixels show what resolution the camera is capable of taking photos, that is, how many millions of pixels the final image will consist of.

Today, many manufacturers present smartphones with 48, 64 or 108 megapixel cameras that operate in dot merging mode. In such sensors, the pixels do not consist of four, but of 16 subpixels, combined by four. Whereas in a classic sensor, for example, one pixel consists of one blue, two green and one red subpixels, in high-resolution cameras it consists of four blue, eight green and four red subpixels.

By increasing the number of pixels, the light sensitivity increases and the dynamic range of the image grows - the difference between the darkest and lightest areas in the photo. But at the same time, 48 megapixel cameras, due to such a combination, in fact create images with a resolution of 12 megapixels. And there is nothing wrong here: this is the case when quantity turns into quality, and pictures with a resolution of 4000 × 3000 (those same 12 megapixels) are quite enough for publication on social networks.

Sensor size

This is perhaps the most important element of a smartphone camera. The size of the sensor indicates the area over which the light-sensitive diodes are located. The larger the sensor, the larger the pixels themselves can be, and the larger the pixel, the better it picks up light. Typical pixel sizes in modern mobile camera sensors are from 0.8 to 2.4 microns, however, the latter is precisely achieved by combining subpixels, which we talked about in the previous paragraph.

The more light the sensor can capture, the better the images captured by the camera will be. This is especially important when shooting in low light conditions. And in such a situation, it may turn out that a sensor with a smaller number of larger pixels will produce a better image than a sensor with a larger number of smaller pixels, because each photodiode has caught more light and, accordingly, more information.

That is, a camera with fewer pixels in its specifications can outperform a camera with a huge number of pixels due to the fact that the pixels themselves are larger.

In modern smartphones, the dimensions of the sensors are indicated in fractional parts of an inch. The largest sensor - the 50-megapixel Samsung ISOCELL GN2 - is installed in the Xiaomi Mi 11 Ultra: its diagonal is 1/1, 12 inches.

Lenses

The lenses used have a significant impact on image quality. They consist of lenses - transparent plates with certain optical properties. The main function of a lens is to correctly distort the incident light beam. The type of distortion depends on the shape of the plate.

Lenses are most often made up of multiple lenses, as one is not enough. Curved and concave lenses of different densities alternate with each other. Correct selection and placement in the lens will affect image clarity and contrast. With curved lenses, optical distortion can occur. In some lenses, such as wide-angle lenses, distortion, on the contrary, has become a stylistic feature. True, some devices programmatically correct them at the post-processing stage.

In modern smartphones, camera modules consist of several lenses, each of which has its own sensor, suitable for a specific task. Most often these are standard, wide-angle and macro lenses. At the same time, it cannot be said that smartphones with several lenses obviously shoot better than with one: it depends on the implementation of a particular device. It may happen that among the many cameras in one module, none will give an acceptable result and the quantity will not turn into quality.

Focal length and aperture

The lower the focal length, the higher the angle of view of the lens, and vice versa - lenses with a high focal length shoot far, but at the same time with a small angle of view.

The aperture shows how much light hits the camera's sensor through the lens. Most smartphones have a fixed aperture, which is the ratio of the focal length to the size of the camera inlet.

The more light hits the sensor and the larger the camera's inlet, the shallower the depth of field, that is, only the subject will be in focus, and the background behind it will be blurred.

To increase the depth of field, you need to reduce the inlet, however, this will also lower the brightness. In smartphones, this is most often achieved programmatically. However, modern devices use modules with several lenses - with lenses of different sizes, different focal lengths and apertures. So instead of relying on software processing, you can switch between lenses.

Smartphones today are equipped with advanced autofocus systems. For example, in PDAF technology, some of the points on the camera sensor are used as focal points. Two adjacent pixels are located so that one of them perceives the light flux coming from above, and the other - from below, and the system adjusts the focus if different amounts of light fall on the pixels.

There is also laser and contrast-based autofocus. Some companies use technologies in cameras that allow you to focus on specific objects in the frame, for example, recognize faces and make them clearer.

Zoom

Zoom shows how close the image can be. There are two zoom options: digital and optical. Digital simply enlarges and crops the full-size image. The optical lens uses special lenses for magnification, which, due to the correct lens system, can look far away.

With the development of cameras in smartphones, more and more modules with optical zoom have begun to appear - usually 2X or 3X. However, there are also options that manufacturers call periscopes. Such lenses use a system of lenses and mirrors located sideways in the body of the smartphone, and due to them, you can get, for example, a fivefold zoom. How close you can get to the image depends on the focal length.

The maximum optical zoom that smartphones offer today is 10x. It is found in Huawei P40 Pro + (it is in it that the same "periscope" is used) and in individual lenses of the Samsung Galaxy S21 Ultra. For those cases when such a strong zoom is not needed, these smartphones also have lenses with a lower magnification - three times.

Auxiliary sensors

Light sensors, depth sensors, rangefinders, lidars - all these systems help the smartphone understand where the objects being photographed are located, how they are illuminated, whether they are moving or not. The smartphone uses the obtained data both in the viewfinder and in the post-processing process, completing and editing the image.

The resolution of the sensors is far from the most important parameter: a very small number of pixels is enough for them to perform their functions well. Therefore, you should not be surprised to see, for example, a depth sensor with a resolution of 2 megapixels: there are enough of them for its operation.

Video Resolution and Frame Rate

Video resolution indicates how many pixels will be contained in one frame. And the frame rate is how many such frames per second will be taken.

As the pixels grow, the detail and clarity of the image improves. As the frame rate increases, the blur effect decreases, the video looks sharper and is better perceived by the human eye. What's more, video captured at high frame rates can then be slowed down to the familiar 24fps for an interesting slow-motion effect.

HDR

HDR stands for High Dynamic Range, which is a large difference between the darkest and lightest parts of an image. The camera in HDR mode takes several pictures (in the case of video shooting - frames) with different exposures and then combines them, balancing light and dark areas. Due to this, it is possible to achieve a higher contrast and image detail.

Post-processing magic

The dry characteristics of smartphone cameras are, of course, confusing and frightening. And the main problem is that it is unrealistic to understand solely from these numbers how the smartphone camera will shoot.

In addition to the system of lenses and sensors around the camera, there is also a harness from the image processor and post-processing software - algorithms that analyze the received data and use various proprietary enhancers. As a result, companies using the same sensors can end up with completely different images due to different post-processing systems.

Each manufacturer has a different approach to color rendering and analysis of object boundaries. Each company uses a variety of tricks and technologies in order to end up with an image that matches their sense of beauty. Some brands use machine learning to correctly identify objects in the frame and how they should ideally look, and this is all part of the processing too.

Let's take a simple example among fairly popular smartphones. In Realme 7 Pro and Samsung Galaxy M51, the main cameras are built on the same sensors - Sony IMX682. It is a 64-megapixel sensor powered by Quad Bayer sub-pixel aggregation system and produces images with a resolution of 16 megapixels (but also capable of working in full-size mode). Despite the fact that they have the same sensors, the images themselves are completely different.

Samsung's color rendition in daylight is more juicy and vibrant, albeit without excessive oversaturation. Photos from Realme 7 Pro received a slightly softer and more realistic gamut, but sometimes the boundaries of small details are lost in them, for example, individual blades of grass, shot relatively far away. At Samsung, the post-processing and noise reduction system defines the boundaries more clearly, which, however, sometimes creates a feeling of artificiality. Confusing the photos taken with these phones will not work, despite the same sensors.

How post-processing of images works on a particular phone cannot be understood from the characteristics. Only professional reviews with test photos taken in various modes will help here.

No faith in megapixels

Specifications do not guarantee picture quality. It cannot be argued that a 108 megapixel camera will shoot better than a 64 megapixel camera, because in addition to megapixels, other camera parameters also affect the result.

The first step is to pay attention to the size of the sensor: the larger it is, the more light it receives, and the image quality directly depends on the amount of light. Next in importance is the hardware part of the image post-processing system, and then the software. How they work can be understood only by seeing the pictures taken by a phone with this system.

The only option is to trust the reviews, which publish test photos in different shooting conditions: under different lighting conditions, in motion, at different distances, and so on. And do not forget that the main tools of the photographer and the operator are straight arms and the ability to capture the moment. And the rest is secondary.