Selecting a ROI using tools on a zoomed image, graph scaling bug or feature

I am leaning to use Igor and I have come across the following odd behavior. I tried searching to see if it had been reported before with no luck.

I want to select a ROI using the polygon tool for later image analysis. Copying the examples from the manual works fine except the roi axes values do not match the displayed ones (the ones on the clicked plot). Detailed explanation below.

I have an image (say 1000x1000 points), I display the image with user selected axes, for instance displaying only 500x1000 of the points. If I now select the ROI on the 'zoomed' image, the polygon tool fills in the roi correctly and it all looks great. However, when I display the M_ROIMask after creating it with ImageGenerateROIMask, the scaling on the x axis is as if I were plotting 1000x1000 rather than the 500x1000 that the selection was made on. Is there a simple fix for this? It is very probable that in real use I will not want to have to display all the data while setting the ROI. Do I have to scale the wave on the axis to correct it or is this a bug/undocumented feature? If I do have to scale the ROI, what is the best way to do that? It is not obvious to me.

Thanks

Philip