Canon : The World of Canon CMOS Sensors


	The image quality of digital photos is determined not only by the number of pixels a camera has. The size of the sensor itself is important, especially for digital SLR cameras. In general, if two sensors have the same number of pixels, the larger sensor offers higher image quality because its sensitivity and dynamic range are higher. Better background blur can also be expected from a larger sensor because its depth of field is smaller. With a lineup ranging from 35mm full-frame to APS-H and APS-C sizes, Canon selects the ideal sensor for each of its cameras, taking into account user needs and the camera's development concept.


	A large CMOS sensor offers better image quality than a smaller because the larger may contain bigger-sized pixels. The relationship between image quality and pixel size can be readily understood if you imagine the pixel as a kind of bucket used to collect not water but light. This micron-sized bucket not only gathers light but also has a photodiode that stores an electrical charge.

Bigger pixels offer higher sensitivity
A regular bucket with a larger opening can collect more water in a shorter time than a smaller one. This is similar to the larger CMOS sensor compared to the smaller: the large one gathers more light in a shorter time and therefore can respond more sensitively.

Large-capacity pixels for wider dynamic range
Wide water buckets of greater depth hold more and have less spillover. In the same way, a larger pixel gathers more light with little or no waste. In CMOS sensors, minimal light overflow and greater capacity mean a wider dynamic range for more subtle gradations, especially in highlight areas. A CMOS sensor with extensive overflow will produce blowout. Smaller pixels are therefore more prone to blowout than larger ones.

Note: Dynamic range is a measure that indicates the scale of fine gradations being preserved from highlight to shadow.

Better S/N ratio from large-capacity pixels
Given two differently sized pixels handling the same amount of noise, there will be less noise impact on the resulting image of the larger pixel. Since larger-sized pixels catch more light, the signal carries more data than noise within the overall image information. This results in a better signal-to-noise ratio, which is particularly effective for fine gradation in low-light shots.

Note: S/N ratio is a measure indicating optical signal purity. The higher the S/N ratio, the smaller the amount of noise and, therefore, the signal may be described as one of high definition.

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