雙影 may be caused by either the shutter speed too slow or mis-focus.
The shutter speed will be slow if the light is dim. To have a clear picture, the minimal shutter speed for most people is 1/60 second with a regular lens at 60 mm or shorter. If you use the lens at 100mm, then you need 1/100 second to get a good picture.
Mis-focus also caused by dim light.
Try to use flash of the camera next time, or put the camera on a tripods to stablize the camera.