I think it is quite important that a lot of you boys and girls out there sort out your RVRs and your visibilities. Despite the fact that several of you are using the expression vis/RVR in the same breath, THEY ARE ABSOLUTELY NOT THE SAME THING!
For example, at an airfield with decent lighting a visibility of 200m would probably result in an RVR of 400m. In fact, under the Old Queen, we were allowed to double reported visibility at night to arrive at an RVR at airfields which could not report RVRs.
What I am driving at (just in case the penny has yet to drop) is that if you land at an airfield quoting an RVR of 1800m and you only have an IMC rating then you are likely to be breaking the law for your restriction is 1800m Visibility and not 1800m RVR.