Reader Dave asks:
“I have a technical question about sensors and pixels… I understand that larger sensor sizes gather more light and thus are better in low light situations and that more pixels will help make a sharper picture… but why do too many pixels make noise and what is the perfect balance? I.e. how many pixels would be good to have on a 1.6 cropped frame sensor?”
Well, the perfect balance will be a challenge. But indeed, this is a balance. Make the sensor larger and you get less noise. Make it smaller with the same number of pixels, and you get [corrected:] more noise. It is not “too many pixels” that make noise. It is “too many pixels stuck together into a small place, meaning they are small pixels”. The smaller you make a phototransistor, the more noisy it gets. So the more pixels you stick in a given area, the more noise.
So to reduce noise you can increase the sensor size, or reduce the area.
- Canon have reduced the pixel count on the G11 compact camera from the G10. Fewer pixels in the same area sensor gives you less noise.
- My 1Ds MkIII creates less noise than the 7D. They have about the same pixels, but a larger sensor (the 1Ds is full frame, the 7D is 1.6 times smaller) means less noise.
Does that make sense?