Hi I figured this out for my case: ptpcamera used around 13-18% CPU time. I had just flickr upload BETA installed today.
Ma Iphone6 was connected via USB.
So what I did was to disconnect the iPhone USB from Macbook Air Early 2015 and voila PTPCamera dropped to insignificant CPU time usage.
Possible causes:
1/ Flick Uploadr was using the service continuously as it is constantly checking for changes in Photos Library. However, when I paused it nothing happened to ptpcamera process, it was still frying my CPU
2/ ptpcamera process is constantly checking USB connected iPhone / iPad for new photos, or media
I am on El Capitan Beta 3
Hope this helped.