Of course subject luminance range can be measured with a spotmeter. In fact, you can only assume the range with an incident meter. There's an interesting paper by Jack Dunn entitled Expose for the Middle where he talks about how an incident meter is perfect for the criteria of the transparency.
Originally Posted by jdef
When you are talking about the curve you are talking about the range of exposure (H) usually referred to as log-H range or sometimes LHR. LSLR basically becomes the log-H range in the camera. Your right in thinking that the two are associated with each other.