I couldn't believe my luck finding this application. But I find I am not able to understand the interface to achieve what I want. Which is:

What images in location A are also in location B?

It tells me duplicate within A and within B but not between the two!
It finds JPG files when all images are selected but not when JPEG is selected!

Setting up duplicates in the same location are not detected by Selecting Images, All kinds in Basic Mode. Selecting the folder and Search. Nothing found even though the selected folder has two folders containing duplicate JPG files! Hmm What did I do wrong there? Do the same with Other files and packages, All file types and they duplicate JPG files are found.
Repeat that selecting two volumes with known duplicates between them but not within them and no items are found.

I've experimented for an hour or so with strategies but still no success. The application is obviously very powerful and I hope to grasp it eventually. I have got some results but I'm unconfident why. JPEG filter does not allow JPG files for example.

For now though I'm unable to achieve what I want. So I will not buy until I have.