I have a problem when using UE4, when I am in the preview mode with lighting on everything looks fine, when I press play everything goes blurry.
This isn’t restricted to a single project, the two that I have going are both suffering from this, they worked a couple of hours ago, I came back to them and they are looking strange.
I don’t remember changing anything but something is obviously different.
I’ve tried messing with AA and screen scaling and nothing has changed.
Go to Settings>Engine Scalability Settings and check the “Resolution Scale” slider. It looks like that has been set at about 75%, which means your game is being rendered at 75% the native resolution and scaled up (this often causes a huge performance boost). Try cranking it back up to 100%.