I'm just curious .. I've started fiddling with CHDK and am trying to learn how to make scripts in uBasic.

Problem is - the wiki's resources are confusing, contradictory [especially], and incomplete.

I've tried looking at example scripts but certain functions I'm looking to use [such as forcing a specific shutter speed and aperture] are simply not used in any of the scripts I've looked through so far. All of them work on automating the choosing of such values rather than forcing them.

I'm experiencing a great deal of confusion over what actual functions are valid or not - given the existence of, say, set_tv and set_tv96 and other related funtions which are incompletely described and the use of which appears to produce no results whatsoever.

Maybe I've just been away from programming for too long, but the [English] references [at least] are insufficient for me to figure out how to do what I want.

If anyone can lend any advice on this, I'd appreciate it.

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Specifically what I'm trying to do is this.. some of the steps may seem extraneous but I'm starting off by making no assumptions as to camera settings. The purpose is to do bracketed night photography in a city setting, where the usual range from street lighting and the like is usually fairly consistent. My camera is an A590is and I'm using the beta CHDK for firmware 1.01b [which may in fact be part of the issue].

1. force zoom to the widest setting [this works]
2. force aperture to the lowest setting [this does not work, trying to use simply set_av and other variants]
3. force focus to hyperfocal distance [this works]
4. force ISO to the camera's lowest standard setting [this appears to work]
5. take 4 exposures forcing the shutter speed to 8, 3.x, and 1 second(s) followed by a 1/250th to balance out in-frame light sources [this does not work at all, whether trying set_tv or set_tv96 or any other related things I see in the reference, all the camera ever does is shoot the already-set shutter speed - noting that I'm in manual mode]

This was my intended goal, to simply force all the settings, leaving fancy stuff until after I've learned what in my mind would be the simplest point to start. Given the many other user scripts I've looked at so far, this assumption of mine is quite wrong, since what I would refer to as the more complicated things actually seem to work just fine.