A method of adjusting video image data to reduce PSE triggers, the method comprising: analysing a sequence of m video images to determine a number of occurrences of a change in brightness between contiguous video images that exceeds a predetermined threshold and determining if said number of occurrences is greater than a predetermined value, wherein the predetermined value is defined over a predetermined time or over a predetermined number of contiguous video images; and if the determined number of occurrences exceeds the predetermined value then applying a correction procedure to the sequence of m video images, characterised in that the correction procedure comprises: for each of the m video images: applying n changes of image brightness, and after each change in brightness is applied to each video image:: reanalysing the sequence of m video images to determine an updated number of occurrences of a change in image brightness between contiguous video mages that exceeds the predetermined value; subsequently determining, based on the reanalysis, which of the n changes of image brightness applied to which of the m video images result in the number of occurrences of a change in brightness between contiguous video images exceeding the predetermined threshold being reduced to below the predetermined value; and modifying the sequence of m video images by selecting the determined change in image brightness applied to the determined video image having the smallest change in image brightness. analysing a sequence of m video images to determine a number of occurrences of a change in brightness between contiguous video images that exceeds a predetermined threshold and determining if said number of occurrences is greater than a predetermined value, wherein the predetermined value is defined over a predetermined time or over a predetermined number of contiguous video images; and if the determined number of occurrences exceeds the predetermined value then applying a correction procedure to the sequence of m video images, characterised in that the correction procedure comprises: for each of the m video images: applying n changes of image brightness, and after each change in brightness is applied to each video image:: reanalysing the sequence of m video images to determine an updated number of occurrences of a change in image brightness between contiguous video mages that exceeds the predetermined value; applying n changes of image brightness, and after each change in brightness is applied to each video image:: reanalysing the sequence of m video images to determine an updated number of occurrences of a change in image brightness between contiguous video mages that exceeds the predetermined value; subsequently determining, based on the reanalysis, which of the n changes of image brightness applied to which of the m video images result in the number of occurrences of a change in brightness between contiguous video images exceeding the predetermined threshold being reduced to below the predetermined value; and modifying the sequence of m video images by selecting the determined change in image brightness applied to the determined video image having the smallest change in image brightness.