Nuso

thank you--you have clarified many things for me, and showed me that I hadn't been reading that Apple page properly

That Apple forum is old--doesn't apply under El Capitan. So far as I can tell, Affinity relies on Image Capture, and Image Capture may not have been updated for El Capitan, hence for certain scanners, like mine, it's broken. So sadly it seems that I can't use Affinity for one of the things for which I bought it.

I can still scan into Acrobat and Photoshop. All the drivers are current. I uninstalled and reinstalled the device in Printers & Scanners, where it's scan function no longer shows up.

I have just purchased Affinity. My Canon MP800 does not show up in Acquire image