This is for the Gamecube version of the game.
Made using DolphinFX v2.10 from the following page:
https://github.com/Asmodean-/dolphin/commits/master
Visit the following thread for DolphinFX installation/usage and help:
https://forums.dolphin-emu.org/Thread-dolphinfx-post-processing-suite-for-the-opengl-backend
To make widescreen work correctly you need to first enable cheats and the widescreen hack (also force 16:9 aspect ratio). Then right click on the game in Dolphin and go to properties, and then edit the config. Then copy and paste the following into it:
For Metroid Prime Pal version :
[ActionReplay_Enabled]
$WS
[ActionReplay]
$WS
0432D7A0 38600001
0432D7A4 4E800020
0432D800 38600001
0432D804 4E800020
0432D86C 38600001
0432D870 4E800020
0432D95C 38600001
0432D960 4E800020
0432D9A4 38600001
0432D9A8 4E800020
For metroid prime NTSC version :
[ActionReplay_Enabled]
$WS
[ActionReplay]
$WS
04344fcc 38600001
04344fd0 4E800020
0434502c 38600001
04345030 4E800020
04345098 38600001
0434509c 4E800020
04345188 38600001
0434518c 4E800020
043451d0 38600001
043451d4 4E800020
Widescreen will reduce performance.