noisy surface

[nodar1978]

Hi guys, when I do rendering in radiosity, usually plane,(wall) which is front of lights (for example daylight or sunlight) always has a noisy surfase as it shown on a images I attached here, please have you got any idea, which parameter makes it smooth in radiosity?

I know there are much more better possibilities in vray and mental ray, but at the moment I don’t have time to read tutorials and doing experiments with renderings, I’ve got 3 project together and I have to finish them as soon as possible.

Thank you