Is it possible to turn the screen off when in call?

[twilk]

I used advance confige tool and set the light sensor to

Light sensor polling: enabled
Light sensor polling interval: 500
Light sensor threshold: 10
Light sensor threshold to turn screen off: 10

Not sure if thats what this is even for but can someone explain this light sensor feature to mean and possible give me a better description of what the light sensor threshold's mean? Also is setting them high make them more sensitive to light getting in or less sensitive?

Thanks guys.