Hi,
Try this - open your un-stretched image (it should mostly be black with very little detail). Open the following processes, "Screen Transfer Function" and "Histogram Transformation" You can leave "Track on" and "Preview" checked. Click the "reset" button on both processors. Now on the STF uncheck "Link RGB Channels" then click the "Auto Stretch" button (Radio-active icon)" if the suggested stretch looks good then click and drag the "execute triangle button" to the bottom bar of the HT process. This will transfer the STF values to the HT process. Here you can tweak the settings and now apply the HT to your un-stretched image.
Look up
John