Optimizing the performance for Dishonored 2Start of by fixing the general performance of the game to get started in fixing the FPS drops. The Texture Quality, RXAA and View Distance seems to have a way to heavy importance on the performance of the game, so we suggest that you start by lowering one, two or all of these and see if the game improves the performance.
Lower the amount of pre-rendered framesDishonored 2 have way too many pre-rendered frames, and lowering the amount of these will dramatically improve the performance. This is done from your graphic card setting, not in the game itself, so exit the game and do the following:
For NVIDIA: Open NVIDIA Control Panel, go to Mange 3D Setting, go to Program Setting and Select Dishonored 2. Here you select either 1 or 2 for the value of "Maximum pre-rendered frames", and the game will improve.
For AMD: You need to download a program called RadeonPro to manually alter the pre-rendered frames setting. Click on the link above to download the program, and find the pre-rendered frames setting from the program. Set the value to either 1 or 2.
RadeonPro is free to download and use, and is very useful to optimize the game performance for any game.
Fix Mouse SmoothingDishonored 2 completely lacks any default mouse smoothing, which means that turning around int he game will dip the FPS dramatically, so you definitely want to fix this. It's not possible to fix from inside the game, because the settings lacks this option for some strange reason. It is however possible in the config-files, so close the game, and locate your save file. It should be somewhere like this:
\Saved Games\Arkane Studios\dishonored2\base\dishonored2Config.cfg
Open this in notepad or another good text editor (I do not recommend using Word or anything "heavy" like that), and use the search function to find the value "g_mousesmooth". The original value will be 1, but chance this to 0. This will fix the problem. Now save the text file, and right click on it. Click on the box that says "Read only", because if you don't do this, the game will overwrite the setting when you start the game again, and it won't work.
Fix low priority settingsWithout manually changing it, Dishonored 2 will be automatically set to be on low CPU priority, so it will not run good at all. Fix this by opening Task Manager (Ctrl+Alt+Del) and go to Processes. Locate Dishonored 2 and right click to chance priority to high.
Fix Render Scale / Adaptive ResolutionThis is the last fix for now, and this is most likely cause by a bug, so if you don't want to wait for a patch to fix your FPS issues, keep reading. The Render Scale makes the FPS drop very low, and this is the most important setting to fix. Open the game and go to Settings. Change Render Scale / Adaptive Resolution from the default 75 to 100. This will stop the game from constantly trying to rescale your game to fit your monitor, and instead use the default monitor resolution.
If you are using a slow, old computer, this last fix might actually make it worse, because this setting is intended for low-end computers to use for playing smoothly. However, it causes problems for good computers, so set it to 100 if you are on a decent computer.