How to Solve Atelier Bells Puzzle
When you enter the Atelier, the main attraction here will be the giant painting of Lady Dimitrescu. This painting is actually a door that has a hidden area behind it. To access this area, you need to complete the bells puzzle, which is to ring each of the five bells hidden here.
The first bell can be found on a table, where you can shoot it once with your pistol to ring it. Once rung, it will be lit by a small flame on top of it. The second bell can be found to the right of the painting, on top of the cabinet.
The third bell is inside the swinging mechanical machine that will be on the left wall from the painting. The swinging motion will eventually reveal the bell inside which is also swinging around. When it comes in your line of sight, shoot at it to ring it.
Now head over to the stairs opposite the painting and stand on the small gallery that overlooks the whole room. You will see a glass ceiling above the painting, while another bell outside in the distance. Shoot the glass ceiling and then at the bell far off in the distance. The final bell is inside the chandelier on the ceiling, which you can spot from the stairs. The bell is sneakily hidden behind and can easily be overlooked, but from your last position, you can shoot it and ring it.
When you have rung all the bells, the painting will open up like a door and will reveal the hidden area for you to explore.