Render result is noisy

[paulvanchugov]

Here is the image https://www.behance.net/gallery/21520825/Room-with-insulation-in-the-slice

 

I rendered it to the 18 sl in 3096 px resolution.

 

Overall picture is fine, but if you look at zoomed version you can see some noise.

 

400% zoom

 

Maybe i make some mistakes with camera settings? And it's noisy partly because of camera focus? To be honest, i can't really see what would render be at the end until i render it.

 

You can see where is the focus in the daylight version.

 

My problem is "target distance" settings and low sl, guys?