DFAO fade out distance?

Greetings,

My scene looks cool with DFAO enabled, but when I zoom out alot, the effect start to fade out and the environment lighting becomes flatter. Is there a way I can control this? My scene will be a large city so I need the effect to be visible.

Please note that my application is not a game, but Arch viz.

Thank you!

Any help??

bump would like to see an answer for this