In case any body has been confused by the Olympus Exposure Comp and Flash Comp settings, I performed some experiments with my EM5, clip on flash and FL-600R. If any of this is obvious to you, that's great. It wasn't to me. Bottom line: EC does nothing in Aperture Priority with TTL metering. FEC appears to affect the overall metering. Linking FEC to EC in the menu basically allows you to adjust FEC directly from your control dial rather than having to go into the Super Control Panel. Since with TTL, I'm constantly adjusting my exposure with FEC, this was a great revelation. I'll be leaving FEC+EC on permanently now. Now I can control ambient light with the Aperture selection, and flash fill with EC. Simple.