hi guys, I am new to photography and looking for an economical flash. I have a Canon 40d and I love it. I am looking for a flash that I think the proper term is e ttl 2 I am not quite sure what that means. But I think it has something to do with my camera automatically adjusting my flash settings. I want a flash that I can control from the camera and that has the ability to go wireless, I'm looking to spend about $100 for this. I saw on Amazon there are some pretty good yongnue flashes. I am just not sure which one will work with my camera. these were the few choices I was looking at, can someone please let me know if these will work with my camera so I can control the flash with my onboard LCD screen. And if it will work wirelessly if I buy the adapter for my camera as I do not think my camera has a built-in.