iPhone X photo preview different from result I would like to know if the camera behavior I am experiencing it's normal or if there is a problem.

When I shoot a photo in low light conditions the photo "preview" I see in the camera app is really different from the final photo.

This is before taking the photo. As you can see there is some noise in the picture:


This is the result taken from the camera roll. The noise is not present anymore and light is totally different:


How it is supposed to work? Because if the preview it's different from the result I cannot trust the preview and maybe I can do some adjustment before shooting (e.g. change the exposure) that will led to a completely unexpected result.
The final photo is not a “screenshot”-esque result, but a processed image.