Steven Spielberg used his iPhone to help create 'War Horse'.

The Oscar-winning director admits he discovered the importance of working with horses while taking pictures with his cell phone, as it taught him the importance of shooting the equine stars of the film in full to capture their moods.

He said: "When I realised I was about to direct 'War Horse', I actually went out to the stables and I just stood out there with my iPhone and I just started photographing the horses from all angles. I tried to see how many expressions I could get out of these.

"And when I realised I couldn't get expressions, per se, from the eyes and the face of the horse I realised by standing back that the horse expressed himself in his entire bearing. So I spent a lot of time with that iPhone trying to figure out how to shoot the horse."

Steven case relative unknown Jeremy Irvine to play the leading human part of Albert in the World War I-set movie, and he believes he will follow in the footsteps of greats including Christian Bale and Drew Barrymore who he has discovered before.

He told "When I found Christian Bale he was so honest, I couldn't deny the fact that there was an actor in this kid. Drew Barrymore, Henry Thomas, there was an honesty with them in 'E.T.'. I just look for authenticity. Are these kids real, and will they convince you lot that they're real? And he was. Jeremy was the most real kid we saw. And also the horse liked him a lot. The horse helped."