However, determining how to use CHDK to reliably manually focus a camera's lens can be difficult as many cameras need to be configured a little differently. This applies to both the "set_focus()" command in CHDK scripts, or the "Override Subject Distance" menu item in the CHDK's Enhanced Photo Operations menu. This problem is caused by there being no standard method that works for every camera that allows you to enable manual focus using CHDK. Some cameras will immediately focus whenever a set_focus() script command is issued or SD override via menu..