A software routine that is activated in Photoshop. Although some plug-ins come with Photoshop, there are countless third-party products that enhance an image in some manner, which would otherwise be tedious or extremely difficult using the regular Photoshop tools. Photoshop "filters" change the appearance of a photo by merely running the filter on the image. Photoshop "actions" enable a series of changes to take place one after the other on an image. See Photoshop actions and image filter.