So with El Capitan , every time you attach an iOS device or a memory card, the Photos app auto launches.
This can be annoying when managing many iOS devices. You can stop this on a device by device basis but is a bit of a pain.
This quick command line, courtesy of Ben Fon will disable it for all iOS devices and memory cards.
defaults -currentHost write com.apple.ImageCapture disableHotPlug -bool YES
To re-enable this feature enter
defaults -currentHost write com.apple.ImageCapture disableHotPlug -bool NO