expl0itfinder :
This is because you need to dedicate a hard drive to your recording software. When you record, it puts a lot of stress on the drive. You are easily be writing more than 50MB/s to the drive. Now on top of that, the drive has to juggle Windows, and BF3. So you are basically getting a bandwidth bottleneck. If you grab a second 1tb hard drive, and just use it for recording, everything will be much smoother.
You are wrong!
I have the same system as he!
But i have 3 hard drives!
1 SSD where battlefield is
1 HDD for programs
1 HDD for recs
BF3 lags when im recording too...
It was a cpu problem!
BF3 is an intensive CPU game !
Screenrecorders use CPU + RAM + HDD!
You can see in any other game that you will record with no problems. Using the same HDD for gaming and recording!
Example : Grid 2!
It is a problem with the game
It eats so much CPU that is impossible do Record with a i5 !
I have a MSI gtx 770 gaming ed
i5 3570k @ 4.6 Ghz, and still get insane fps drop when recording!
Hope you can understand my engrish x)