Choosing the Optimal Sensor for Low Light Photography: 24MP BSI-CMOS vs 20MP CMOS

The decision between a 24MP BSI-CMOS (Back-Side Illuminated Complementary Metal-Oxide-Semiconductor) sensor and a 20MP CMOS sensor with varying pixel pitches in low light photography can be intricate. Both options have distinct advantages and considerations that photographers must evaluate. In this article, we'll break down the key differences to help you make an informed decision.

Understanding Sensor Performance in Low Light

When it comes to capturing images in low light, one common metric is pixel size, as larger pixels generally gather more light and are less prone to noise. However, the practical difference in low light performance between these two sensor types is likely to be minor, according to most expert opinions. This is because most sensor quality tests are conducted at high resolutions (100 view or larger), a process known as "pixel peeping," which doesn't accurately predict real-world performance.

Theoretical Differences: Pixel Size and Area

To better understand the theoretical differences, let's dive into the mathematics involved. The size of the pixel is a critical factor as it directly influences the amount of light the sensor can capture. We can calculate the area of each sensor by multiplying the number of pixels by the square of the pixel pitch.

Calculating Sensor Area

The area of the 24MP BSI-CMOS sensor, with a resolution of 6000 x 4000 pixels and a pixel pitch of 2.95 μm, is:

[ text{Area} 6000 times 4000 times (2.95 , mu m)^2 8.47 , text{sq cm} ]

The area of the 20MP CMOS sensor, with a resolution of 5472 x 3648 pixels and a pixel pitch of 5.94 μm, is:

[ text{Area} 5472 times 3648 times (5.94 , mu m)^2 8.63 , text{sq cm} ]

Given that the 24MP sensor has a smaller number of pixels compared to the 20MP sensor, the latter has a larger surface area, which theoretically means it can collect more light for the same exposure time, leading to slightly less noise.

Considering Actual Performance Factors

It's important to note, however, that these theoretical differences may not always translate to noticeable performance improvements in real-world conditions. This is due to several assumptions and variables that must be taken into account:

Sensor Manufacturing Process: The 20MP sensor being larger doesn't guarantee better performance if it is manufactured using a less sophisticated process compared to the 24MP sensor. Deposition of Silicon: The way silicon is deposited and structured can affect noise levels and light collection efficiency. Post-Capture Electronics: The electronics surrounding the sensor, such as processors and noise reduction algorithms, play a significant role in overall image quality. Signal Processing: Advanced signal processing techniques can mitigate the effects of smaller pixels and potentially enhance low light performance.

Conclusion

Ultimately, the choice between a 24MP BSI-CMOS sensor and a 20MP CMOS sensor with a pixel pitch of 5.94 μm largely depends on your specific needs and preferences. While the 20MP CMOS with a larger pixel pitch has a theoretical advantage in terms of light collection and noise reduction, the practical difference might be so subtle that it doesn't significantly impact your results in low light conditions.

However, always consider factors such as the manufacturing process, the quality of the post-capture electronics, and advanced signal processing techniques. These can often provide a more significant contribution to overall image quality in low light situations.

Key Takeaways

BIS-CMOS sensors generally have a better light-gathering capacity due to their pixel design. Larger pixel size reduces noise and enhances low light performance. Practical differences in low light performance may be minimal, depending on other factors like manufacturing process and post-processing techniques.

By carefully considering these factors, you can make an informed decision that best suits your photography needs and the specific conditions under which you plan to shoot in low light.