Sir Ian McKellen gets ''increasingly depressed'' about his acting ability if he has to reshoot scenes.

The 73-year-old star - who plays Gandalf in the 'Lord Of The Rings' movie franchise and upcoming 'Hobbit' film series - likes to be told if he is not playing a character as a Director wants him to, but he is often ''surprised'' at the number of filmmakers who don't know how they want movie stars to portray their alter-egos.

He said: ''I like to know what's going on. So if for some reason, the director isn't happy with what he's got, he's only got to say why. 'Well, it's a tricky camera shot, Ian. It's not you, you're fine.'

''Some directors don't tell you that it's not your fault, so you get increasingly depressed that you're not delivering what's required, and then you discover it's not you at all, it's something in the background that's out of focus. I think if I were asked to do as many as 50 takes, I would assume the director had no idea what he wanted, and was just hoping, eventually, to see it. And you would be surprised how many directors don't know what they want.''

While Ian doesn't enjoy being told he's doing something wrong, he had no complaints about reshooting scenes in the 'Lord of the Rings' or 'Hobbit' franchises because he puts his full trust in director Peter Jackson.

He added to Collider.com: ''There can be a bit of politicking going on, but if you trust a director totally, as I do Peter - Peter's never shown any character, any actor, to disadvantage. He's terribly protective of- 'They must be seen at their very best.' And knowing that, and believing that, and having seen it in his work, if he wants me to do 27 takes, I'll do them.''