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s-series - enable flash during video recording for still images (in trunk now!)

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Offline PhyrePhoX

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s-series - enable flash during video recording for still images (in trunk now!)
« on: 14 / October / 2008, 16:03:04 »
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Hi,

this topic is specific to the s-series cameras, which have the ability to take pictures DURING video recording. however flash is disabled. i dont know why exactly canon disabled the flash during video recordings, maybe it is because of power or something along this - i dont know.
But i'd really like to have flash enabled, because i use that to trigger my external flash guns. this way i can make a video of a photosession and at the same time use the "videocamera" to take the real photos. also it is useful for lowlight situations where you have enough light for video, but not enough light for (non blurry) still images.

i tested setting propcase 16 (digicII) during recording - the propcase gets set and stays at the given value (1 in s3is case for ALWAYS ON) but when i press the shutter flash isnt used. in still picture mode this overriding of the flash param works via script (useful for example for DISABLING the flash via script because once you pop up the flash in manual mode it is ALWAYS ON, no matter if you press the dedicated flash button, when you dont want to pop down the flash).

sifting through the s3is dump i see a few functions and names with "flash" in it, dont really know where to start though.
first maybe i wanted to start a discussion on what people think WHY canon built the cams so that they dont use flash during video recording. maybe there are good reasons and its better to not tap into that realm (camera damage anyone?). if there arent good reasons then maybe some more skilled asm gurus can hack something useful together!?

regards, phox
« Last Edit: 29 / November / 2008, 17:08:31 by PhyrePhoX »
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Offline fudgey

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Re: s-series - enable flash during video recording for still images
« Reply #1 on: 14 / October / 2008, 17:08:42 »
My a570is is completely unresponsive after a flash shot. It turns off the LCD and doesn't respond to keypresses other than the rec/play and power switches. It's clearly trying to use all the current it can safely draw from the batteries to re-charge the flash as fast as it can (and still fails to impress...) by disabling all other high current circuits.

I believe the S series is fancier in this regard (can it do a series of small flashes with single charge?), but I wouldn't be surprised if power consumption was the reason. Worst that is likely to happen is camera shutdown due to low battery (and maybe some memory card file system corruption to go with it if you're recording video at the time) if the input current increases above normal, bringing battery voltage down.

I don't see why they'd be charging the flash from the regulated logic voltages, so the power supply/supplies should be safe from overheating...

Should be particularly smooth if you can find a way to make a partial discharge to trip your external flashes.
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Offline PhyrePhoX

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Re: s-series - enable flash during video recording for still images
« Reply #2 on: 14 / October / 2008, 17:38:53 »
just tested flash output in continuous mode: at low power level i can go pop pop pop pop ... 20 exposures with flash, felt like 2 pops a second, didnt time it though. i guess i could have gone even further (more than 20 i mean by that, didnt test it). with the power set to the middle setting it is more like one shot every 1 second. camera set to manual focus, continuous. there is no difference in "lag" after a shot depending on flash or not (means i instantly see either the review or the normal camera osd) - on the s3is at least (i even turned off review time to make sure). only lag is induced by "recharging", but that wouldnt be an issue to me.
did you try that in low flash output as well (in MANUAL flash mode of course)?
still the reason could be powerconsumption, as in recording a movie there is a constant powerdrain (writing i&o and what not). well, if i override that "check" that checks if a video record is in progress and disables the flash - i guess worst that can happen is cam shutdown, like you wrote. thanks for your informative post fudgey :)
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Offline fudgey

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Re: s-series - enable flash during video recording for still images
« Reply #3 on: 14 / October / 2008, 18:58:49 »
Yes, I can get continuous mode flash shots at lowest flash power setting, something like 1,5 s apart (crude approximation, significantly slower than without flash anyway but fast enough to be useful, thanks for making me try ;) ). But it's not consistent (I think it only works well if the flash cap is full when shooting starts AND if battery is reasonably full).

Lowest flash power is pretty weak, though... in a dimly illuminated room I got shots of furniture 2 m away from the camera underexposed by 3 Ev using F2.6 ISO800...

During continuous shoot with flash it doesn't turn off the LCD between shots, but it does after releasing the shutter (as it does in single shot mode). The unresponsive flash recharge time after releasing the shutter is significantly longer than the delay between shots in continuous mode, btw, except in full flash power mode, where they are approximately equal, 7 seconds or so.
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Offline PhyrePhoX

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Re: s-series - enable flash during video recording for still images
« Reply #4 on: 16 / October / 2008, 03:41:57 »
Quote
Lowest flash power is pretty weak, though... in a dimly illuminated room I got shots of furniture 2 m away from the camera underexposed by 3 Ev using F2.6 ISO800...

well lowest power is enough to trigger my flashes (either by optical fibre cable or my s3is gobo/modifier :D)

will do some more tests on the "unresponsiveness" and probably look deeper into the dump, maybe i can find something. would really like that \o/
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Offline dzsemx

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Re: s-series - enable flash during video recording for still images
« Reply #5 on: 16 / October / 2008, 05:38:32 »
only 2 AA battery powered cameras turns off the screen if flash capacitor has been (almost) totally discharged.
my a630 and a650 can shoot in continous mode with flash like S series cameras.
only I can't take pictures (but everything else works)  until flash has been charged (a630 max 5 sec, a650 max. 6-7 sec), no screen turn off.
i would be happy if i could tweak flash recycle times, especially at a650, to reduce at least at 5 sec
« Last Edit: 16 / October / 2008, 06:03:31 by dzsemx »
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Offline fudgey

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Re: s-series - enable flash during video recording for still images
« Reply #6 on: 16 / October / 2008, 18:07:33 »
That freeze is really very annoying... The camera is able to charge the flash slowly in the background without freezing the user interface because if I'm not mistaken, that's what it does if I enable flash, fiddle around for a while and then shoot -- flash is ready to fire without hesitation.

But after a flash shot the camera decides (without asking me for permission >:() that the next thing I want to do is to shoot again as quickly as possible. Well guess what, I almost never do, because there's almost always a little something to fiddle (like looking at the image in play mode or adjusting exposure or flash power...something that takes more than 7 seconds allowing for slower reload, but what I can't start doing it until 7 seconds has passed).

A "Single No-Reload Flash Mode" would be precious for me. Actually that mode would even save some battery life, because if I only take one shot and it's good, I wouldn't need to waste energy recharging the flash at all. This is something CHDK might be able to help with...depends on how quickly after shooting the camera decides to recharge and what does it take to disable flash at that point. Maybe setting digic3 prop143=2 in RAW code would suffice...

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Offline PhyrePhoX

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Re: s-series - enable flash during video recording for still images
« Reply #7 on: 16 / October / 2008, 18:20:56 »
Yeah, might be worth tapping into. Also flash bracketing springs to my mind ;)
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Offline c2thew

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Re: s-series - enable flash during video recording for still images
« Reply #8 on: 17 / October / 2008, 22:37:55 »
might freeze your camera forcing you to turn it off and on like the md lightning script does.  hopefully you guys can get the flash to sync with video.
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Offline PhyrePhoX

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Re: s-series - enable flash during video recording for still images
« Reply #9 on: 29 / November / 2008, 17:08:11 »
the solution to this is now in trunk: #603 thanks to the help of ewavr.
power isnt an issue here by the way. i dont know why canon disabled this. i really dont know it. maybe because automatic flash power cant be calculated? but this cant really be the reason...
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