The experimental, amateur-built airplane was a high-wing pusher-propeller configuration, with the engine mounted above the wing. The private pilot reported that he had a total flight experience of about 154 hours, including about 36 hours in the accident airplane. The preflight inspection, engine run-up, and takeoff were normal. After the pilot leveled the airplane in cruise flight at an altitude of about 1,300 feet above the ground, he gripped the control stick with his legs in order to free his hands to access and use a camera for some aerial photography. The pilot had done the same thing on previous flights, and he was aware that the airplane had a tendency to pitch down and accelerate when not monitored and controlled continuously. After he took some photographs, he grasped the stick with one hand and applied back pressure to reduce the airspeed. He tried to stow the camera with one hand, but let go of the stick to complete that task. The airplane descended and accelerated again, but to a higher airspeed than the previous time. Although the control stick was free to move, the pilot was unable to correct the flight path with the elevator, and stated that within "a few seconds the aircraft was pointing near[ly] straight down." He deployed the ballistic recovery parachute, and then retarded the engine to idle. The airplane impacted terrain nose-first and sustained substantial damage. The still-inflated parachute dragged the airplane across the ground until the pilot egressed the airplane and collapsed the parachute. Post accident examination of the airplane by a Federal Aviation Administration inspector did not reveal any pre-impact anomalies or failures. The pilot reported that after the accident, he learned from other pilots of the accident airplane make and model that it was necessary to retard the throttle in order to successfully recover from a dive.