"24-70" as in the 24-70mm f/2.8L lens? If so, then it's no wonder you are getting a shadow arc at the bottom of the frame. The built-in flash on the 10D isn't made to work with large lenses (I think it even says that in the manual). The 24-70L has a filter diameter of something like 77mm, right? The lens is so "fat" that it sticks up into the light path of the flash. Canon probably thought that anyone using the 10D and high-end prosumer/pro lenses would be using an external flash. For the Digital Rebel (300D), they set the internal flash higher. Probably thinking that more point-and-shoot/medium digital camera users would be likely to buy that camera and even if buying L glass, they would be more likely to use the internal flash (since that's what they're use to). Though, I've never seen anything that says whether or not the higher position of the flash helps with the big lenses -=>Donald