Pas de problème sur le 50D.
Pour les Ifbagor/Ifbagon, voici une réponse que j'avais eue il y a quelque temps :
Ifba (and its derivatives Ifbagor, Ifbagon, Ifbaflex, etc.) was a distributor brand available in the "Flash" stores, a chain of photo stores (like Revue or Porst in Germany) that was active in France in the 1960s and 1970s. The rebranded gear was usually made by Tamron, Cosina or Chinon. Flash stores were aggressively distributing their catalog in the mailboxes all around the country. This brand brings back lots of memories. I remember as a teenager I was drooling while browsing through the pages packed with dream cameras and lenses -- would you believe, they even had a 400mm lens... Alas, I had no money to buy this kind of equipment, and I was condemned to spend my weekends on my bicycle shooting all around Paris with my modest Voigtländer Vitoret loaded with Ilford HP4...

Here's a link to a page about Flash on a French site: Appareils photo anciens : Fex Ultra-Fex

Le site de fondus de MF Lenses où j'ai eu cette réponse :
Manual Focus Lenses :: View topic - IFBAGOR 35 & 135
Bon amusement.