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King Arthur was filmed on location in Ireland. However, the weather and landscape did not meet the need for an icy expanse.

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Computer matte paintings create the snowy valley while film of a fine spray creates the foreground mist.

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One of the film's most spectacular scenes was a fight on a frozen lake......

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....but it took visual effects to give the film the look it needed.

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Great shots of Ireland's landscape were used throughout the film.

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But sometimes a few tweaks had to be made.

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This shot of Arthur, played by Clive Owen, is bleak - but not bleak enough for the film-makers.

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The computer supplies the moutainous backdrop and gives the actors a more wintry feel.

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Actors stand in a field firing arrows - but what are those green screens?

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The location is suddenly more menacing thanks to visual effects.

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Keira Knightley shows off her archery skills.

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Her rosy complexion is removed inside a computer.

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The snow on the ground is merely paper, while those green hills are simply not suitable.

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The snow is made more icy and the green fields are replaced by snow-filled crags.