Okay, I have a Canon XTi, and I have 3 Vivatar 285 HV's. Oddly I am having problems with only one scenerio, and that is if I have one flash mounted on my hotshoe on the camera and I take a photo, half of my photo turns out fine, and then the other half turns out pitch black. Why is this occuring?!?! Is it because the flash mounts so high on the camera? what is happening? the onboard flash works fine, so it obviously my external flash issue.