I have just tested four Canons P&S's. I can set up a scene - and at ISO 400, AV mode, f 2.8, all the cameras decide this should be shot at 1/30th.
If I try the exact shot with an a650 with CHDK, it wants to take this same shot at *1/15th*.
In every case, it wants the shutter open for twice as long twice on the a650 compared to these others. If I double the ISO on the a650, then all shutter speeds match.
Either the a650 reports all ISOs far from actual value, or something else is up that is confusing me.
In every case I tested, it looks like the older cameras need half the light that an a650 seems to need. The a650 shots look great, but this still seems rather odd.
If I enable the CHDK "show real iso" it shows Canon 800 as 523 - have I screwed up a setting? I don't think I have any overrides set anywhere..
Is this not a CHDK thing? Any info would be a big help.