After many problems with my the infrared trigger to fix sony nex decided not to have problems with my orthophotos.
I modified the trigger of the camera soldering two wires as this website says. http://photoshipone.com/10/sony-nex5n-trigger-modification/
(I'm not having pictures of my installation sorry)
then later connect the two wires to solder on my trigger and connect the output relay of pixhawk.
it set to trigger remote is made through relay with mission planner.
and this is the result!