Abstract
Many different performance measures are used to characterize x-ray optics, sometimes resulting in radically different rankings. This makes it difficult, even for practitioners intimately involved in the field, to compare results from different optics and for different applications. To truly understand and appreciate advances in a specific type of optic – polycapillary optics – different methods of optic comparison are evaluated and their relevance explained. These methods include transmission efficiency, flux, flux density, equivalent distance, normalized gain, insertion gain, and effective capture angle. Polycapillary focusing optics with varying input and output parameters are compared using these different performance standards.