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Problem with external flash

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Offline frandom

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Problem with external flash
« on: 24 / February / 2009, 17:59:22 »
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Hi all,
first of all I want to thank the CHDK team, I love it!

now the problem:
my G9 has a curious behaviour of CHDK with external flash.
Once ext flash is mounted in the hot shoe the camera overrides the CHDK time settings.
e. g. In Manual mode I set shutter speed 1/200, then  in CHDK I set 1/10,000 in "Override shutter speed value" but the camera shoot at 1/80!
Is there a way to use high shutter speed with an external flash?

Thanks

F.random

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F.random

Canon G9 - 100d
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Offline fudgey

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Re: Problem with external flash
« Reply #1 on: 25 / February / 2009, 13:59:03 »
Are you sure the shot was really taken at 1/80 s?

EXIF Tv field shown by the camera and most image processing software is false when CHDK overrides are used. The correct Tv can be found encoded in the Canon MakerNotes section of the same tag, though.
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Offline frandom

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Re: Problem with external flash
« Reply #2 on: 26 / February / 2009, 10:28:59 »
Quote from: fudgey on 25 / February / 2009, 13:59:03
Are you sure the shot was really taken at 1/80 s?

EXIF Tv field shown by the camera and most image processing software is false when CHDK overrides are used. The correct Tv can be found encoded in the Canon MakerNotes section of the same tag, though.

How can I read correct this Canon MakerNotes. I have an EXIF viewer but in MakerNotes section, Exposure Time is "192"! What does it mean?

F.random
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Canon G9 - 100d
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Offline fudgey

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Re: Problem with external flash
« Reply #3 on: 26 / February / 2009, 13:45:32 »
exiftool -MakerNotes:ExposureTime IMG_0001.JPG
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Offline frandom

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Re: Problem with external flash
« Reply #4 on: 27 / February / 2009, 10:40:03 »
Thanks for your tip, it confirm the behaviour I supposed: CHDK can't override shutter speed with something in hot shoe.
In G9 hot shoe there is a little switch that, I guess, activates this safe mode.

That's my test:
manual mode
Canon Tv: 1/100s
CHDK Tv: 1/10,000s

with external flash mounted, Tv: 1/25s
without external flash, Tv: 1/10173s

F.random
« Last Edit: 01 / March / 2009, 16:08:46 by frandom »
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F.random

Canon G9 - 100d
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Offline PhyrePhoX

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Re: Problem with external flash
« Reply #5 on: 27 / February / 2009, 12:24:30 »
thats odd. might also explain the problems we have with the s5is and the flash.
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Offline wontolla

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Re: Problem with external flash
« Reply #6 on: 27 / February / 2009, 13:54:40 »
I run these two commands just after the pictures have been copied to PC:

exiftool -overwrite_original "-exif:ExposureTime<MakerNotes:ExposureTime" -r .
exiftool -overwrite_original "-exif:iso<iso" -r .

This is to copy "Exposure Time" and "ISO" from MakerNotes to EXIF fields. So when I open them in Lightroom or whatever the actual values are shown.
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Offline pecas

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Re: Problem with external flash
« Reply #7 on: 10 / November / 2009, 19:54:47 »
I have the same problem with my G7. I've been trying to use the hack underwater with a external strobe (ikelite) conected in the hot shoe and the overrides don't work, it seems that the camera uses the predefined settings depending if you are using TV, M or AV.
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