The script should run on any CHDK equiped camera that has an ND filter. It does not use key presses or propset values. The only adjustment available is an exposure offset. The script first takes a picture with normal exposure settings and then inserts the ND filter and takes a second shot with the same exposure settings. The second shot will always be darker than the first. You might need to adjust the normal exposure level if this sequence does not work for you. Info on ND filter :