Was using my friend's Sigma EF 500 flash and realised that when in the AV mode, the camera trigger the flash but the shutter speed is not syncronized.

That is to say the metering says 1/4 sec, and it shoots at that shutter speed.

Wheareas with the built in flash, it automatically changes to shutter speed for the flash taking.

Also when I in menu to set up the external flash, the ETTL-II option and curtain option are greyed out? Is it because the flash do not support ETTL-II.

Thought of getting the newer Sigma EF-530 DG Super for myself but was afraid that the same may happen.

Can help?