Let’s talk about sensor sizes!
Sensors have different sizes, as you can imagine by taking a look at the different camera sizes and models.
The smallest ones are smaller than a fingernail and have the same 12MP resolution as a APS-C (22,5 x 15,0 mm) sensor built in in a semi-pro DSLR.
The smaller a sensor is, the higher is the effort required to amplify the information it gathers from the scene it is photographing. But more calculation leads to more errors, which means more noise.
The bigger a single physical “pixel” on a sensor, the less noise it produces. Take a look at the different sensor sizes.
(graphic above from wikipedia.org)
—-
(first contribution from Martin, edited by Mareen)

