Lithographic method and apparatus

A lithographic apparatus comprising a projection system configured to project a pattern from a mask onto a substrate, the lithographic apparatus further comprising:

• a sensor configured to measure an aberration caused by the projection system and/or the mask used by the lithographic apparatus, wherein:
• an aberration signal obtained from the measured aberration comprises a first component and a second component,
• the first component of the aberration signal comprises a first frequency band and the second component of the aberration signal comprises a second frequency band, and
• the first frequency band comprises frequencies that are higher than frequencies comprised in the second frequency band;
• a processor configured to calculate a correction to be applied to the projection system, wherein the processor is configured to calculate a first part of the correction based on the first component of the aberration signal after using a filter to apply a weighting to the aberration signal;
• and
• lens manipulators configured to apply the correction by manipulating lenses of the projection system.