Image sensor CMOS vs. CCD: How much impact does target surface size have on image quality?
The difference between the two working principles
CCD is a "charge coupled device". The charges generated by the pixels need to be transferred row by row to a unified output node and then amplified. Therefore, the consistency is good and the noise is low, but the process is complex, the cost is high, and the power consumption is high. CMOS is "complementary metal oxide semiconductor", An amplification circuit is integrated next to each pixel, which can directly read the voltage signal, and the cost and power consumption are much lower.
In the early years of CMOS, due to individual differences in each pixel amplification circuit, the picture noise and consistency were not as good as CCD. However, as back-illuminated (BSI) and stacked processes mature, CMOS has completely surpassed it in terms of low illumination and dynamic range. At present, almost all security cameras use CMOS, and CCD only exists in a few industrial and scientific research scenarios.
Why target size is important
With the same 2 million pixels, the larger the target surface, the larger the area of a single pixel, and the greater the amount of light that enters. There is less noise in low illumination. This is why "the same nominal value is 0.001Lux, but the actual effect is much worse."
| Target surface specifications | Common positioning | Low illumination performance |
|---|---|---|
| 1/3 inch | Entry model | The noise is obvious at night and needs supplementary light |
| 1/2.8 inches | Mainstream models | With a large aperture, it can meet most scenes |
| 1/1.8 inch | Mid-high-end | Low light picture is clean and details are well preserved |
| 1/1.2 inches and above | Flagship Starlight Level | Can still image in near-lightless environments |
Suggestions for selection
- In indoor passages and lobbies with stable lighting, 1/2.8 inches is enough, so put your budget on the lens and installation location.
- In low-light scenes such as perimeters, parking lots, and lightless corridors, give priority to target surfaces of 1/1.8 inches and above, which is much more effective than stacking "software noise reduction".
- Be sure to read the test conditions (aperture F value, whether to turn on fill light, and AGC status) for the "minimum illumination" in the parameter table. The calibers marked by different manufacturers vary greatly and cannot be directly compared horizontally.