Even if you have recently taken up photography, you have probably heard such a thing as “Digital noise” and https://www.artlook.us/service/wedding-photo-booths-nyc/, but if you didn’t hear it, then you saw it for sure. Perhaps you called it grain, dust, sand or something else. But the essence remains the same. The photo looks terrible.
Consider the simplest example of digital noise
For example, you took a picture of your girlfriend in the evening on the street and then found that the whole picture is grainy.
You blame everything on your camera for 3000 rubles. and you start thinking about buying a camera for 10,000 rubles, but believe me, this will not solve this problem, since the problem is in setting up the camera itself!
Most camera owners shoot in Auto Point-and-Shoot mode, 
and the camera will set everything up for you! So, the camera has such a value as ISO, “Sensitivity”, and the grain in the photo is the so-called “digital noise”, and it appears when the ISO in the camera is set to high values - 400, 800 and more. Light sensitivity is the ability of your camera’s matrix to collect light as quickly as possible, and if it is insufficient, the camera will naturally set the value higher, it does not care that the photo will be killed by noise later! My advice is simple: “The more light there is, the less set the ISO” and try never to set its value above 400. In my Samsung soap dish, bought for 1300r on Avito, I always have an ISO value of 100. This camera I gave a friend’s wife as a gift, but the settings remained) And now she thinks that this is the best camera she ever had, because before, when shooting with ISO in auto mode, she got noisy photos, but now their quality is noticeably better, and She doesn’t even know why!