how to over ride shutter settings - General Help and Assistance on using CHDK stable releases - CHDK Forum
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how to over ride shutter settings

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Offline kosherbacon

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how to over ride shutter settings
« on: 15 / August / 2008, 22:38:02 »
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So I'm pretty new to this, and I don't really know what everything means. So if someone could explain it all to me it would be great. I'm looking at the menu "extra photo Operations" and I don't know what anything means. What I really want to do is photograph water drops, but I don't know what settings would be good or why they would be good.
So yea, any help would be great.
Thanks!
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Offline fe50

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Re: how to over ride shutter settings
« Reply #1 on: 16 / August / 2008, 06:14:53 »
Hello & welcome kosherbacon,

you can read all about the CHDK usage here: CHDK wkia: CHDK firmware usage/AllBest.

For waterdrops you'll need the fastest shutter speed, use a tripod & use the flash...see also CHDK wikia: Samples: High-Speed Shutter Flash-Sync.
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Offline kosherbacon

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Re: how to over ride shutter settings
« Reply #2 on: 16 / August / 2008, 23:51:08 »
So I tried to change it and I'm not sure that it worked.
I changed....
Override shutter speed to: 2
Value Factor to: 1/100K
Shutter speed enum type to: Factor

I press the shutter button
I get a message that says "***Started*** This is a default script Scripts run when shutter button is pressed in alt mode. Press shutter to exit." And then every time I press the shutter button it shows that and wont take any pictures.
Am I missing something?
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Offline fbonomi

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Re: how to over ride shutter settings
« Reply #3 on: 17 / August / 2008, 04:46:21 »
You pressed "Print" and you got in Alt mode, where you have the CHDK menu

But in Alt mode all buttons have different functions, including "Shoot", that now does not shoot but runs the loaded script.

You have to press the "Print" button to get out of alt mode, then the buttons will have their usual fmeaning, and the camera will shoot, but with the overrides
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Offline kosherbacon

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Re: how to over ride shutter settings
« Reply #4 on: 19 / August / 2008, 08:33:42 »
So I tried and with the flash on it was really bright and with the flash off it was really dark. So I'm guessing it's working and I just need more light when I do it. Right?
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Offline fbonomi

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Re: how to over ride shutter settings
« Reply #5 on: 19 / August / 2008, 09:18:25 »
well, I guess so!
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Offline kosherbacon

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Re: how to over ride shutter settings
« Reply #6 on: 19 / August / 2008, 09:23:48 »
 :D
Thanks for all your help!
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Offline kosherbacon

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Re: how to over ride shutter settings
« Reply #7 on: 19 / August / 2008, 13:33:05 »
So I've tried a couple of shots and it's really giving me some trouble. It's still either really bright or really dark. In re-reading the article mentioned above (multiple times to try and understand it) It talks about changing the flash output. Is there a way to change that on a Cannon Powershot SD450? Or is that a certain thing in CHDK that I'm just missing?
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Offline fe50

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Re: how to over ride shutter settings
« Reply #8 on: 19 / August / 2008, 14:31:16 »
Quote from: kosherbacon on 19 / August / 2008, 13:33:05
So I've tried a couple of shots and it's really giving me some trouble. It's still either really bright or really dark. In re-reading the article mentioned above (multiple times to try and understand it) It talks about changing the flash output. Is there a way to change that on a Cannon Powershot SD450? Or is that a certain thing in CHDK that I'm just missing?

I wrote the following in the feature request section:

Quote
Quote from: fe50 on 18 / August / 2008, 18:59:44
harvald,
do you mean "dimming" / adjusting the flash ?

I'm not sure which camera you're using, but this should work in a script with set_prop of the properties
#15, #28 & #29      (Digic II)  or
#121, #127 & #141 (Digic III) - this works on the Ixus 860.

If the flash intensity can be controlled by this properties it could be integrated in the CHDK menu...it's also implemented in the SDM, at least for the Ixus 860...

So you can do some tests with a script & these props...you can also try a "hardware mod": use toilet paper or sandwich paper to to soften the flash  ;)
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Offline whoever

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Re: how to over ride shutter settings
« Reply #9 on: 19 / August / 2008, 15:02:29 »
Quote from: kosherbacon on 19 / August / 2008, 13:33:05
So I've tried a couple of shots and it's really giving me some trouble. It's still either really bright or really dark. In re-reading the article mentioned above (multiple times to try and understand it) It talks about changing the flash output. Is there a way to change that on a Cannon Powershot SD450? Or is that a certain thing in CHDK that I'm just missing?
When you shoot with flash and want to freeze the fastest motion, it's not the shutter speed but the flash duration that matters. The latter is (roughly) proportional to the flash power. Thus, you either set the flash power to minimum if your cam allows it (if it doesn't, there is a CHDK workaround through propcases, see the post above), or else you just use auto flash, which at short distance will adjust itself to the minimum possible power. But it'll still be too bright, if you are really close. It's this overexposure that you can compensate with "extra-fast" shutter override (you have to experiment and find the right value), but don't fool yourself into thinking that that "extra-fast" setting actually determines the shot duration -- it doesn't, as long as it is outside certain limits (usu some tenths of ms, but you have to determine the exact value for your cam). Else -- an on-flash diffuser, e.g. toilet paper, as suggested above.

edit: typo
« Last Edit: 19 / August / 2008, 15:19:42 by whoever »
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