Why is Image Capture showing two copies of every photo in my iPhone camera roll?
I just had this issue and found a solution on another site:

First, close Image Capture. Next, dismount the iPhone from the Mac by ejecting it with iTunes and unplug the cord from the iPhone. Then, just plug it back in and open up Image Capture again. 

Worked for me - only one set of images.

Of course, this was after trying a couple other things... like turning off My Photo Stream (Settings>iCloud>iCloud>My Photo Stream: OFF) and turning off the "Keep Normal Photo" option (Settings>Photos &amp; Camera>Keep Normal Photo: OFF), but I didn't notice any change immediately after doing these things  Only after unplugging and reconnecting the iPhone did the problem fix itself.  GOOD LUCK!