With thanks to "Ruined", a member of the nvnews forums, he's spent some time posting up a guide which explains how to go about enabling a feature by the name of High Dynamic Range (or "HDR" in short) lighting which is included within the latest 1.3 patch for FarCry (released just yesterday). The trickyness in enabling it is due to the fact that it's covering new ground as an 'unsupported beta' feature at this stage.
If you're wanting to know how it affects the visual experience of the game, you'll be glad to know the guide also includes a mass of before and after screenshots showing off it's effects. Unfortunately there's a couple of letdowns, the biggest being that only the GeForce6 family of graphics cards currently have the ability to make use of it at this stage. Second of all, lovers of antialiasing will be dissapointed to make note of the fact that AA must be completely disabled for OpenEXR HDR lighting to work.
HOW TO ENABLE HDR
Nvidia GeForce 6 card
DirectX 9.0C (included in SP2)
Nvidia 61.77 or later drivers
FarCry 1.3 patch
1. Set all Graphic settings to "Very High."
2. Anti-Aliasing must be disabled.
3. Add:"r_hdrrendering 7" "e_vegetation_sprites_distance_ratio 100.000000" "r_TexNormalMapCompressed 1" with the quotes to your farcry shortcut. For example:
"C:\Program Files\FarCry\Bin32\FarCry.exe" "r_hdrrendering 7" "e_vegetation_sprites_distance_ratio 100.000000" "r_TexNormalMapCompressed 1"
4. I recommend lowering your resolution to 1280x1024 or 1024x768 depening on CPU & GPU core speed. 1280x1024 is more appropriate for high speed athlon 64 CPUs with 6800U (or 6800GT @ 6800U) while 1024x768 works better for lower end P4 CPUs with 6800GT @ stock speeds.