Hey I am a Mac user and I randomly pressed up against a button on my keyboard and it so happens when I press the button 'control' it zooms me in and has that smooth turn when you press F11 I believe it is . If you have a Mac start up your Minecraft and test it out ^_^
Are you using Optifine? I know when I have Optifine enabled, pressing CTRL (on windows) causes it to zoom in and turning while zoomed has a smooth swaying effect.
Yup, optifine it's the one that does that, the minecraft 'as is' doest. pretty nice tool to record stuff
I don't know cause I am using one of Twitch1's .jar lol xD he emails it to me when I request it hes a good friend