Vision: Do you see grainy images especially when you look into dark or is my vision faulty?

When I look into dark area like night sky or outdoors at night or a dark room, the image appears grainy (somewhat similar to grainy images of digital cameras,
example 1-less grainy
2-more grainy
3-most grainy
3 is much more grainier and 1 is slightly less grainier than what i am talking about

But its not there only in dark spaces- generally if i am looking at low detailed places with homogeneous colors, then the grainy effect is pronounced. With increasing brightness and more detail, the graininess of the images becomes less and less perceivable.

So, please look into dimly-lit/dark spaces around you and tell me if what you see appears ‘grainy’, and if so, whether that effect persists when you look in bright spaces with low detail

Do you know what I am talking about??