It’s not the sensor size they matters (larger sensors actually have more noise: that’s why phone photos can look as good as they do). Stop and think for a second: where does the extra light captured by a larger sensor come from?
What actually matters is the physical aperture of the lens. What a large sensor forces you to do is use a larger physical aperture to get the same focal ratio (“f-stop”) and field of view. That’s how you get more light. (the larger physical aperture and constant focal ratio implies a longer focal length, so the math works out)
If you do the math, the larger physical aperture more than compensates for the extra noise of the larger sensor (signal to noise of the system scales as sqrt(sensor_dimension)), so camera systems with larger sensors and the same focal ratio have better noise figures. But it’s not directly due to the sensor.
You can compensate for a lot of that effect by simply installing a lens with a larger focal ratio on a small sensor. That’s because it turns out to be easier to have a high focal ratio when the lens is small: the shorter focal length (for a given field of view) requires a smaller radius of curvature, so controlling chromatic aberration and circle of confusion is easier at higher focal ratios.
It’s not the sensor size they matters (larger sensors actually have more noise: that’s why phone photos can look as good as they do). Stop and think for a second: where does the extra light captured by a larger sensor come from?
What actually matters is the physical aperture of the lens. What a large sensor forces you to do is use a larger physical aperture to get the same focal ratio (“f-stop”) and field of view. That’s how you get more light. (the larger physical aperture and constant focal ratio implies a longer focal length, so the math works out)
If you do the math, the larger physical aperture more than compensates for the extra noise of the larger sensor (signal to noise of the system scales as sqrt(sensor_dimension)), so camera systems with larger sensors and the same focal ratio have better noise figures. But it’s not directly due to the sensor.
You can compensate for a lot of that effect by simply installing a lens with a larger focal ratio on a small sensor. That’s because it turns out to be easier to have a high focal ratio when the lens is small: the shorter focal length (for a given field of view) requires a smaller radius of curvature, so controlling chromatic aberration and circle of confusion is easier at higher focal ratios.