When I plug my iPad in, Photos opens. I want it to stop opening when I plug it in. To make it stop, write a disableHotPlug key into com.apple.ImageCapture as true:
defaults -currentHost write com.apple.ImageCapture disableHotPlug -bool true
To enable Photos opening when you plug in a device again, just delete the disableHotPlug key:
defaults -currentHost delete com.apple.ImageCapture disableHotPlug