I am using a600D with it's inbuilt flash. When I try to take a photo in dim using the flash, in priority mode, the camera chooses a very slow . It seems as if it ignores the fact that I have the flash popped-up. This causes the resulting photo to look like 2 superimposed pictures, one nicely exposed via the flash, but the other image is like a ghost from when I inevitably move the camera a bit during the long .
What is the right setup to take the photo?