I own a K-M 7D and typically don't use flash. However I'm attending a 'must record' function that will need flash more powerful than the built in one. In all probability anything I get will then sit in the cupboard, unused, for a long time. I don't know anyone from whom I could borrow a suitable flash.
Here's the question then. What's the cheapest flash that will work on 'auto' on the 7D and give me a modicum of control?
Here is the Sony flash compatibility chart (applicable to your 7D I think). Only the Minolta flashes with D suffix will work properly - the others were designed for film cameras and, although they will fire, won't give the correct exposure without setting the camera to fully manual and working out your own exposure. The Sony ones with AM suffix will also be fine.