When you play the game on a higher resolution, sometimes it will be messed up, and crop the bottom and right of the screen entirely. This can really easily interrupt your gaming experience, because if you don't know how to fix it you will have to play on a lower resolution. That means blurry textures and all that.

This fix also applies to Penumbra: Necrologue, which requires Amnesia: TDD to be installed. It doesn't have a separate exe, so you only need to fix the Amnesia application in the following steps, and the games in Necrologue will be fixed as well.

Right-click on Amnesia: The Dark Descent from your Steam Library, choose Local Files, and then click Browse Local Files. This will take you to the location of the game files via Windows Explorer.

Find the Amnesia application. Not sure if the Amnesia_NoSteam below works too, but probably not. Right-click on it.

From the right-click menu, click on Properties, and then click on the Compatibility tab. Click on the "Change high DPI settings" and it will open a new window.

On the new window that opened, tick the box beside "Override high DPI scaling behavior" and set the scaling performed by Application. Click OK on that window, and then Apply on the Properties window. Now launch the game.

The resolution should be working properly now. Have fun!

Here are some screenshots from Penumbra: Necrologue's main menu to show the difference. Left is before and right is after.

There has been several users telling about this weird fix in the discussions forum, which is not fixed by a reinstall or verifying game files. But the discussion that I used in particular was this one.

Hope this helps you! Have fun playing the games.