A complete guide to the purchase of a dash cam: a multi-dimensional in-depth analysis

1. Introduction

In today's increasingly complex transportation environment, driving recorders have become essential equipment for many car owners to protect their rights and record their driving history. However, facing the dazzling array of dashcam products on the market, it is not easy to choose a product that truly suits oneself and has excellent performance. This requires us to conduct in-depth consideration from multiple key dimensions, including aperture size, HDR (high dynamic range) and SDR (standard dynamic range), anti exposure and anti darkening functions, polarizers, image sensors, and processors. This article will explore in detail the impact of these dimensions on the performance of driving recorders, providing a comprehensive purchasing guide for car owners.

2. The size of the aperture value

aperture value is an important indicator of the amount of light entering a lens and is usually expressed as an f-number. For example, f/1.8, f/2.0, etc., the smaller the value, the larger the aperture, and the more light enters. In a dash cam, the size of the aperture directly affects its ability to shoot in different lighting conditions.

(2) The advantage of large aperture

1. Night shooting performance

wide aperture has a significant advantage in night driving records. When driving on dimly lit roads, such as country lanes or poorly lit city streets, a wide aperture allows more light to enter the lens, resulting in brighter shots. This helps to clearly record information such as road conditions, surrounding vehicles, and pedestrians, greatly improving the ability to record safety at night. For example, a dash cam with an aperture of f/1.6 can capture more detail than a product with an aperture of f/2.2 when shooting at night, such as traffic signs in the dark on the side of the road or the silhouette of a parked car on the side of the road.

2. Imaging quality in low-light environments

in low-light environments, such as entering an underground parking lot or in the evening, a wide aperture reduces noise caused by poor light. Noise can make the picture look grainy and blurry, which can seriously affect the clarity and legibility of the video. By increasing the amount of light entered, the image sensor can receive more light signals, thereby reducing the possibility of noise when over-amplifying the signal to improve brightness, and ensuring the purity and delicacy of the picture.

(3) Applicable scenarios and limitations of small aperture

small aperture is relatively small, it also has its effect in some specific scenarios. For example, in strong light environments, such as when direct sunlight shines during the day, a small aperture can reduce the amount of light entering the lens, prevent overexposure due to too bright the picture, and allow the captured picture to retain more details. However, in most daily driving scenarios, especially in complex and changeable lighting conditions, a small aperture may cause the picture to be dark due to insufficient light intake, and the shooting effect at night or in low-light environments is often unsatisfactory.

3. HDR and SDR

> (1) Principles and advantages of HDR

1. Implementation of wide dynamic range

HDR technology takes multiple photos with different exposures on the same scene, and then uses image processing algorithms to extract and fuse the highlights and dark details in these photos, so as to generate an image or video with rich details that are not exposed in highlights, underexposed in darkness. In dash cams, the application of this technology greatly improves its shooting capabilities in complex lighting scenes. For example, when driving on a road with both strong sunlight and large shade, or when entering or exiting a tunnel, HDR can clearly show details in both bright areas (such as the sky, pavement in direct sunlight) and dark areas (such as walls in tunnels, objects in shadows), such as signs in tunnels, pedestrians or vehicles in shadows, etc.

2. Color and detail restoration

HDR not only excels in brightness and dynamic range, but also outperforms SDR in terms of color reproduction and detail. It captures richer color layers, making the picture more vivid and realistic. For example, when shooting scenery on both sides of a scenic road, HDR can delicately restore the blue of the sky, the emerald green of the leaves, and the bright colors of the flowers, while clearly showing the texture of the leaves and the details of the petals of the flowers.

(2) Characteristics and limitations of SDRs

SDR, as a traditional video display technology standard, has a relatively narrow brightness dynamic range and limited color depth. In scenes with uniform lighting, SDR can record images normally, but once encountering high-contrast light scenes, such as direct strong light or low light and strong light, it is easy to overexpose highlights or underexpose dark areas, resulting in loss of picture details. For example, when driving at night, when facing the high beams of the oncoming vehicle, the SDR dash cam may make the area around the light white and make it impossible to see other objects in the area. On dark roads, SDRs may not be able to clearly record details at the edge of the road or faintly lit objects in the distance.

4. Anti-exposure and anti-dark functions

(1) Anti-exposure function

1. Principle of exposure control technology

anti-exposure function mainly relies on advanced exposure control algorithms to achieve it. The dash cam's image sensor monitors the light intensity in the frame in real time, and automatically adjusts the exposure parameters when it detects that excessive light may cause overexposure, such as shortening the shutter speed, reducing the aperture size, or reducing the sensitivity of the image sensor. For example, when a vehicle is driving facing the sun, the anti-exposure function reacts quickly to direct sunlight into the lens, reducing the amount of light entering the lens, so that details in bright areas such as the sky and buildings are preserved instead of a white overexposure.

2. Adaptability to different lighting scenes

an excellent dash cam should have an anti-exposure function that can adapt to a variety of bright light scenarios, including direct sunlight and strong light reflections (such as reflections from water surfaces, strong light reflected from building glass), etc. In these scenarios, it effectively controls exposure, ensuring clarity and legibility of the picture. For example, when passing through a road with a large area of water, even if the sunlight generates strong reflections on the water, the dash cam can accurately record the road conditions and surrounding vehicles through the anti-exposure function, avoiding the loss of important details due to overexposure.

(2) Anti-dark function

1. Low-light enhancement technology

Anti-Dark feature mainly uses low-light enhancement technology to improve shooting results in low-light or nighttime environments. This technology includes optimized processing of image sensor signals, the use of special noise reduction algorithms, and appropriate improvement of image brightness and contrast. For example, by increasing the sensitivity of the image sensor to weak light, more light signals can be captured when driving at night, and then using noise reduction algorithms to remove the noise caused by increasing the sensitivity, and finally adjusting the brightness and contrast to make the picture clearer and brighter. For example, on a rural road without street lights, the anti-dark function allows the dash cam to clearly record the direction of the road, the trees on the side of the road, and possible pedestrians or animals.

2. Synergy with other features

anti-dark features often need to work in tandem with features such as large apertures, HDR, etc., to achieve the best low-light shots. The large aperture provides more light inlet, while HDR plays a role in handling low-light scenes with large contrasts of light and dark, and the three work together to shoot high-quality video at night or in low-light environments, providing more comprehensive recording guarantee for driving safety.

5. Polarizer

(1) Principle and function of polarizers

1. Principle of light polarization

polarizers work based on the polarization properties of light. Light vibrates in different directions during propagation, and polarizers can filter out light from other directions by allowing only light that vibrates in a specific direction to pass through. In dash cams, polarizers are primarily used to reduce glare and reflected light. For example, when a vehicle is driving in the sun, the road, window glass, and surrounding buildings produce a large amount of reflected light and glare, which can interfere with the dash cam's capture, making the picture blurry or halo.

2. Improvement of shooting effects

By installing a polarizer, the dash cam can effectively reduce the impact of these reflected light and glare, making the picture clearer and purer. When photographing landscapes, a polarizer can make the sky bluer and white clouds whiter because of its ability to filter out scattered light from the atmosphere, enhancing color saturation and contrast. When photographing road conditions, you can clearly see the details of the road surface, such as road texture, water stains, and traffic markings, and can also more clearly identify the license plate numbers and body characteristics of surrounding vehicles, improving the effectiveness of video evidence.

(2) Precautions for the selection and use of polarizers

1. Adaptability issues

When choosing a polarizer, you need to make sure it matches the lens size of your dash cam. Different models of dash cam lens diameters may be different, and if the polarizer size is not suitable, it may not be installed or will affect the shooting effect. In addition, some dash cams may already have a polarizer function built in, eliminating the need for additional installation in this case.

2. Angle adjustment

polarizers need to be adjusted appropriately according to the direction of the light when used to achieve the best filtration effect. In general, it is necessary to rotate the polarizer to observe the picture in the viewfinder or display, and the best angle is when the reflected light and glare are eliminated to the maximum. However, during driving, there may be certain inconvenience in manually adjusting the angle of the polarizer, so some high-end dash cams may have the function of automatically adjusting the angle of the polarizer, further improving the convenience of use.

6. Image sensor

1. CMOS vs CCD

currently the mainstream dash cam image sensors on the market mainly include CMOS (complementary metal-oxide semiconductor) and CCD (charge-coupled device) types. CMOS sensors have the advantages of low power consumption, high integration, and low cost, and their imaging quality has been greatly improved with the continuous development of technology. CCD sensors excel in imaging sensitivity and signal-to-noise ratio, but they consume more power and cost more. In the field of dash cams, CMOS sensors are more widely used because they can meet basic imaging requirements while better adapting to the low power consumption and miniaturization needs of dash cams.

2. Sensor size

image sensor is also an important consideration. Common dash cam image sensor sizes are 1/2.7 inch, 1/2.9 inch, 1/3 inch, etc. In general, the larger the sensor size, the more light it can capture and the better the image quality. For example, a 1/2.7-inch sensor will shoot better in low-light than a 1/3-inch sensor with less noise and more detail at the same pixel count and aperture size.

(2) The effect of image sensors on image quality

1. pixels vs. resolution

image sensor determines the resolution at which the dashcam captures video. A higher pixel count can capture clearer and more detailed images, and more detail can be recorded. For example, a dash cam with 2K resolution (typically 2560×1440 pixels) can render text and patterns more clearly when shooting distant vehicle license plates or road signs than a 1080P resolution (1920×1080 pixels). However, the number of pixels is not the only factor that determines image quality, and it is also necessary to comprehensively consider the size of the sensor, pixel size, and image processing capabilities.

2. Low-light performance

image sensor is directly related to the effectiveness of the dash cam at night or in low-light environments. As mentioned earlier, larger sensor sizes, higher light sensitivity, and advanced noise reduction techniques all contribute to improving the performance of image sensors in low-light environments. When driving at night, image sensors with good low-light performance can capture more faint light, making the picture brighter and clearer, reducing blur and noise caused by insufficient light, and providing a strong guarantee for driving safety records.

7. Processor

(1) Core functions of the processor

1. Data Processing & Coding

the processor of the dash cam is mainly responsible for processing and encoding the large amount of image data collected by the image sensor. It requires rapid conversion of raw image data into video formats that can be stored and played, such as common encoding formats such as H.264 and H.265. In this process, the processor's computing speed and processing power directly affect the speed and quality of video generation. For example, a high-performance processor can complete complex image data processing tasks in a short period of time, ensuring that the dash cam can record high-definition video in real time and play back smoothly without lag or lag.

2. Feature Support and Optimization

processor is also responsible for supporting and optimizing other features of the dash cam. For example, for HDR functions, the processor needs to run the corresponding algorithm to synthesize images with different exposures; For the anti-exposure and anti-dark functions, the processor should adjust the shooting parameters in time according to the light information feedback from the image sensor. For some dash cams with intelligent functions, such as voice control, motion detection, etc., the processor also needs to process relevant instructions and data to ensure the normal operation and efficient response of these functions.

(2) The impact of processor performance on the overall performance of the dash cam

1. Video Smoothness & Stability

processor performance directly determines the smoothness and stability of dash cam video recording and playback. If the processor is slow, frame drops may occur when recording high-definition video, resulting in incoherent video images. When playing back videos, there may also be lags, pauses, or even inability to play due to untimely data processing. The powerful processor can ensure that the dash cam can stably record and playback video in various complex scenarios, providing users with a good user experience.

2. Function expansion and upgrade potential

a good processor also offers the potential for the expansion and upgrade of the dash cam. With the continuous development of technology, new functions and technologies are emerging, such as more advanced image recognition technology, smarter driver assistance functions, etc. If the dash cam processor has sufficient performance margins, these new features can be added through software upgrades, so that the product will always maintain a certain degree of advancement and competitiveness throughout its service life. For example, some high-end processors support deep learning algorithms, which lays the foundation for driving recorders to achieve intelligent driving assistance functions such as pedestrian recognition and vehicle collision warning.

>8. Conclusion

when choosing a dashcam, dimensions such as aperture value, HDR and SDR, anti-exposure and anti-dark functions, polarizers, image sensors, and processors are all aspects that need to be focused on. A wide aperture helps improve shooting at night and in low-light environments; HDR technology provides richer detail and color in complex lighting scenes; Anti-exposure and anti-dark functions ensure clear recording at different light intensities; Polarizers reduce glare and reflected light interference with shooting; A good image sensor is the foundation of good image quality; The powerful processor ensures the overall performance and functionality of the dash cam. Only by comprehensively considering these factors and weighing the trade-offs according to your actual needs and budget can you choose a dash cam that truly meets your needs and has excellent performance, providing reliable records and guarantees for our driving life.