A Tilt Pair

Drawing of an untilted and the corresponding tilted micrograph
Figure from Frank (1996)

A tilt pair is two micrographs that are directly related to each other through a tilt along an axis of rotation. Tilt pairs are used in electron microscopy to solve one of the basic problems encountered in single particle reconstruction: how to determine the angles φ and θ for the particles.

The field of view is generally very similar and several landmarks within each picture are used to determine the spacial relationships between the two micrographs. In this figure, the untilted image is on the left and the tilted image is on the right. The tilt axis is the dashed, vertical line running along the middle of the right image. Due to the tilted point of view, the particles on the right image a look much different from the homogeneous sample seen on the left image.

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