compare and contrast:
Benedict Cumberbatch in costume versus in character as Sherlock Holmes.
His pose is essentially the same albeit posture, expression, and the way Benedict carries himself in both images show a clear distinction between simply being in costume as compared to playing the part.
In the left image, more natural and candid, in the right image, more calculated and poised. He almost looks more gaunt in the right image as well. Costume notwithstanding, there is a clear distinction between actor and character.
What a great actor. Damn, I hate him so much.