Dhans,
How did you create the Ctl Refnum in "Untitled 8 (SubVI).vi"? I am having the same problem as the OP. I want to be able to pass a reference to an IMAQ image control from a caller VI into a subVI. See my modified version of your example code for the reason why. Right-clicking on an IMAQ image control to create a reference, then right-clicking on the reference and choosing "Create Control" does not create a refnum control. It does nothing. Also, LabVIEW will not allow me to create a subVI of a selected portion of code by using Edit->Create SubVI if the reference to the IMAQ image control is passed into the portion of code I want to create the subVI from. I'm using LV 2019, but have down-compiled the attached example into LV 2014.
Scott
