Roof-prisms designs also require tighter tolerances for alignment of their optical elements (collimation). The line of collimation or line of sight should coincide with axis of the telescope. A laser or synchrotron beam are also often used directly without additional collimation. Among the latter are frame rate settings, pulsed fluoroscopy and collimation. The axis of altitude level must be parallel to the line of collimation. This is why most laboratory small angle devices rely on collimation instead. Otherwise, instrument collimation will be compromised and the resulting measurements would be in error. The vertical circle must read zero when the line of collimation is horizontal. Another tool for decreasing dose is collimation. This would be a creative use of how the term collimation is conventionally understood.