11-22-2018 03:34 PM
11-23-2018 10:58 AM
Canon's ETTL flash system is fairly advanced and it has quite a few capabilities. One capability is to use the system to trigger off-camera flashes (it uses light to commuincate firing instructions to the off-camera flashes). And sometimes a photographer wants off-camera light without the on-camera light in the shot. So it turns out there is a way to do this... the on-camera flash fires to communicate instructions *before* the shutter is actually open. When the shutter does open, only the off-camera units fire.
There is no feedback from the off-camera flash. This means it's possible to get the camera in the mode to control an off-camera flash ... even if the off-camera flash doesn't exist. (it uses light to communicate the instructions ... but it doesn't know there isn't a flash receiving the firing instructions.)
As you look at it, you visually see the flash fire, but you don't see the light from that flash in the photo (it all happens so fast you would never know it technically fired a fraction of a second before the shutter opens).
My guess is you've got in that mode and your pop-up flash is actually firing just before the shutter opens.
See page 178 of your camera's manual... there is an option to clear the flash settings (both for built-in settings as well as for external flash control).
If you've mislaid your manual, you can download a copy here: