Can you try what happens if you use the camera's "long shutter" mode instead of a CHDK shutter speed override?
I've made a new build with disabled support for >64s exposures. You can choose either the diskboot.bin or the ps.fi2 version this time. CHDK-ixus220_elph300hs-101g-1.0.0.zip - 0.35MB
Before i load this new DISKBOOT i tried with DisableOverrides=ON. The ISO and shutter were exactly as set by the Canon f/w (8", iso100) but now I cannot turn off the DFS again...even after resetting everything as it was last night. Maybe I mixed up versions of the DISKBOOT (doubtful) thus good time to try your new one. Thanks...later.
Ok, with the new DISKBOOT I can still get DFS off but only in Program mode, not in Long Shutter either in ALT or not in ALT mode.
What you made work a couple days ago still works:, DFS for long exposures but only in P mode as far as I can tell. Whatever changes are in the new bin do not jump out at me.
Please clarify; what is the difference (other than script execution) of pressing the shutter in ALT mode versus not in ALT? The OverRides still seem to work either way so I wonder what is supposed to be off when ALT is off but was loaded on boot? DFS is still undecided. With the new DISKBOOT I just restarted, set a OverRide shutter of 5", turned ALT to OFF, then fired single shots in Program mode. The first 2 did not use DFS. The next shot, and all afterwards, did use DFS. Nothing else touched in between and lighting was very dark with no changes. I can still get what I need most as long as I start off with Program and ALT turned on.
I am thinking we should take up a collection to send you a spiffy new Elph300HS or whatever its called across the pond. Wish you were closer so I could just send you mine to play with until you tire of it.
Cheers.