The thing to know about Cryis is that it's all about the shadows. Shadow calculations is very CPU intensive and your video card is almost rendering everything twice. The fact that almost everything is casting a shadow is amazing in itself and that the game runs at all. We'll appreciate it more when we upgrade out hardware.
For mid range systems, turn shadows to low. It may say low, but the shadows are off. Yeah, it doesn't look as good but now the game is very playable.
For high end systems, you may need to leave shadows to medium. I'm not sure there's a system right now that can have shadows set to hi and have an acceptable frame rate. If your can, good for you.
To squeeze out a few more fps, turn pixel shaders to low. From medium to low, I don't see any real difference.
Setting any of the other settings to low may squeeze an additional frame but for me it hasn't been worth it.
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