What RtS saidJust a not here, some lenses are set to focus beyond infinity - ie. you will fine a little more distance beyond the infinity marker. This is to allow fo infinity in the infra red spectrum (IIRC)
So if you have no markers focus all the way out then pull back just a little. Using a narrow aperture will account for any small mistakes but you will still get the desired effect![]()
So for example on my 350d (and I think pretty much every camera) you turn the focus ring anti clockwise
By definition you can't focus past infinity!