I think the Baader FFC (Flatfield Corrector) is a barlow. Baader calls it a barlow on their page
And I think it is a barlow because it increases magnification when increasing the eyepiece distance. The FFC can be used from 3X-8X.
However, it has 4 lenses instead of the typical 2 that barlows have. Are the 2 additional lenses only used to create a flat field? Why 4 lenses instead of 2?
Also, I see that some telecentrics can increase power with distance as indicated on TV's page with the 5X Powermate. Or am I misunderstanding the diagram? https://www.televue....?id=53&Tab=_app
Why does the 5X Powermate increase magnification while the others don't or do only marginally?
I couldn't find a ray trace diagram of the Baader FFC.