how can I lock the camera in order to stay aimed to the same object during a manual flight?

You can't during manual flight.  You have to manually aim the camera during manual fight.  There are intelligent flight modes where the Spark will fly for you and keep the camera aimed at a subject.  However, the pilot has to be ready on the sticks to save the bird if it messes up.

rememeber not to double post

Hi there, thank you for reaching out. About your question, Captain @Gunship9 is correct about this. There is no way to lock the camera, however, we have some intelligent flight modes that you can use just to stay aimed at the subject, for example, the quick shot, you may check page #16 on the manual https://dl.djicdn.com/downloads/ ... 0Manual%20V1.6-.pdf about the quick shots. Best regards!