Light Circle on wall

Hi,

i’m newbie to unity and I can handle quality of rendering.
As shown in the image below, I’ve a Spotlight in front of camera and it generate circle on the wall.
I would like to have soft transition between the different circle.
I thought it was antialiasing but I can’t figure out how to manage it
38715-lightcircle.jpg
Thanks for you help

Try to turn HDR on on the camera.