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Force AUTOMATIC flash

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Offline besik33

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Force AUTOMATIC flash
« on: 09 / May / 2009, 20:08:27 »
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It is possible to add option - force AUTOMATIC flash in M mode?

This is quiet useful in macro photography with built in flash, where the power of the flash depends only on the aperture and the shutter is without effect.

MANUAL flash has only 3 steps  :'(, while
Automatic flash has 13 steps.  :o
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Offline fudgey

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Re: Force AUTOMATIC flash
« Reply #1 on: 10 / May / 2009, 07:04:05 »
Are you sure it's the flash that has all those steps and not ISO or Av? Even if there are such steps in flash power, I'm afraid this could be difficult.

Isn't manual ISO in Av mode pretty much the same thing, btw, if it's dark enough and Tv doesn't affect exposure?
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Offline besik33

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Re: Force AUTOMATIC flash
« Reply #2 on: 10 / May / 2009, 18:15:16 »
« Last Edit: 11 / May / 2009, 17:39:46 by besik33 »
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Offline fudgey

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Re: Force AUTOMATIC flash
« Reply #3 on: 11 / May / 2009, 16:40:23 »
Quote from: besik33 on 10 / May / 2009, 18:15:16
Automatic flash has 1 step which can be corrected in 12 steps. So this gives 13 steps for automatic flash.

No, that's flash (auto)exposure correction, not flash power adjust. It's there because autoexposure with flash is wildly different from autoexposure without flash and often much worse in guessing what you want mainly because it's working in the dark. But it can still decide to adjust to one of those 13 steps from available values for ISO, aperture and flash power if shooting mode allows that (M mode doesn't, thus flash autoexposure correction obviously cannot exist).

I'm not saying there aren't more than 3 flash power levels in your camera, just that number of flash exposure correction steps doesn't prove otherwise. To find out if there really are more power levels for the flash you could (if you already didn't) take a series of shots with different correction settings and compare the image exposure and exif (makernotes preferably) for tv,av,iso and flash settings. If you can find more than 3 different exposures with identical Av/Tv/ISO/ND, you're on your way to convince me :D.
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Offline PhyrePhoX

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Re: Force AUTOMATIC flash
« Reply #4 on: 11 / May / 2009, 16:44:55 »
maybe i will add another flash method to chdk, not just the manual one (that already is in the override menu). it is on my list for months now (together with the flash bracketing!). but i dont have much time lately, and to be frank: this isnt top priority stuff :)
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Offline besik33

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Re: Force AUTOMATIC flash
« Reply #5 on: 11 / May / 2009, 21:32:16 »
« Last Edit: 11 / May / 2009, 21:49:36 by besik33 »
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Offline fudgey

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Re: Force AUTOMATIC flash
« Reply #6 on: 12 / May / 2009, 15:18:11 »
Yes I believe I'm sufficiently convinced now... :haha

1) Hm...did you just prove that (if not in M mode) the camera decides flash power after CHDK has overrided Av and Sv?
2) I guess (because I don't know better) that automatic flash power is very difficult to implement in M mode. A finer manual control of flash power in M mode sounds like the logical next step, and in search for that I'd start by trying to find a propcase that correlates with this finer flash power level. From http://chdk.wikia.com/wiki/PropertyCase you can see we already know of several propcases that have something to do with flash (121, 122, 127, 133, 141, 143, 208 for the Digic III propset)... this one should be new, and likely must be read during the shooting process.

If propcase control doesn't cut it, I'm afraid firmware disassembly analysis is required for each and every camera model and fw version, potentially a lot of work with no guaranteed result, meaning an eager & skilled developer is required.
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Offline besik33

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Re: Force AUTOMATIC flash
« Reply #7 on: 12 / May / 2009, 18:48:40 »
TXH for reply.
But sadly, Im not developer. I just can test the avaible functions.
I dont know software  disassemliing.....
and HW disassembly I allredy finished on my dead G7.
http://canon.hostuju.cz/Canon%20G7%20vnitrek%20.php.htm  :lol
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Offline whoever

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Re: Force AUTOMATIC flash
« Reply #8 on: 13 / May / 2009, 12:25:23 »
Quote from: fudgey on 12 / May / 2009, 15:18:11
A finer manual control of flash power in M mode sounds like the logical next step
...
If propcase control doesn't cut it, I'm afraid firmware disassembly analysis is required
Not sure if that's to the point, but see http://chdk.setepontos.com/index.php/topic,2204.0.html
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Offline fudgey

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Re: Force AUTOMATIC flash
« Reply #9 on: 13 / May / 2009, 13:55:36 »
Quote from: whoever on 13 / May / 2009, 12:25:23
Quote from: fudgey on 12 / May / 2009, 15:18:11
A finer manual control of flash power in M mode sounds like the logical next step
...
If propcase control doesn't cut it, I'm afraid firmware disassembly analysis is required
Not sure if that's to the point, but see http://chdk.setepontos.com/index.php/topic,2204.0.html

I believe it's exactly to the point...had forgotten all about that one. From the look of it manual flash duration (read: power) control would be possible but it's a lot of work to find those addresses for all 76(?) firmwares.
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