The present invention relates to a method and an X ray apparatus comprising an X ray source an x ray detector and at least a first collimator having a first active position and a second collimator having a second active position for forming a bundle of X ray beams wherein both of said active positions are located in a substantially straight path between said X ray source and said detector but at different distances from said X ray source. The X ray apparatus further comprises a selector arrangement for switching one of said first or second collimators in said first or second active position whereby when one of said first or second collimators is in an active position the other collimator is in an inactive position.
