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How Canon detect an external flash?

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Offline c_joerg

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How Canon detect an external flash?
« on: 17 / November / 2017, 05:20:43 »
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In notice on my G1x, if I connect the ground of my oscilloscope with the flash rail of the G1x, the camera goes in the condition that there is an external flash (The flash symbol disappears and Exposure Simulation goes off). But always short and not permanent. The same I achieve, if I touch the rail with a key.

My EOS M3 does sometimes do the same but it looks like the M3 is not so sensitive. The different between G1x and M3 is also, that the M3 still made Exposure Simulation.

My guess is that the camera performs a high-ohmic or capacitive measurement here.

Update:
Sorry for the stupid question. I need new glasses. It’s a switch….
« Last Edit: 17 / November / 2017, 08:24:19 by c_joerg »
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Offline c_joerg

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Re: How Canon detect an external flash?
« Reply #1 on: 17 / November / 2017, 08:25:08 »
Quote from: c_joerg on 17 / November / 2017, 05:20:43
In notice on my G1x, if I connect the ground of my oscilloscope with the flash rail of the G1x, the camera goes in the condition that there is an external flash (The flash symbol disappears and Exposure Simulation goes off). But always short and not permanent. The same I achieve, if I touch the rail with a key.

My EOS M3 does sometimes do the same but it looks like the M3 is not so sensitive. The different between G1x and M3 is also, that the M3 still made Exposure Simulation.

My guess is that the camera performs a high-ohmic or capacitive measurement here.

Update:
Sorry for the stupid question. I need new glasses. It’s a switch….
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Offline waterwingz

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Re: How Canon detect an external flash?
« Reply #2 on: 17 / November / 2017, 09:21:43 »
Quote from: c_joerg on 17 / November / 2017, 05:20:43
Sorry for the stupid question. I need new glasses. It’s a switch….
Even better - you can enable / disable that switch from the CHDK menus.  Look for "Hotshoe Override" in the "Enhanced Photo Operations" menu.
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Offline c_joerg

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Re: How Canon detect an external flash?
« Reply #3 on: 17 / November / 2017, 10:29:47 »
Quote from: waterwingz on 17 / November / 2017, 09:21:43
you can enable / disable that switch from the CHDK menus.  Look for "Hotshoe Override" in the "Enhanced Photo Operations" menu.

Thanks, but it looks like that's not supported on G1x and M3 ...
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Offline waterwingz

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Re: How Canon detect an external flash?
« Reply #4 on: 17 / November / 2017, 10:43:22 »
Quote from: c_joerg on 17 / November / 2017, 10:29:47
Quote from: waterwingz on 17 / November / 2017, 09:21:43
you can enable / disable that switch from the CHDK menus.  Look for "Hotshoe Override" in the "Enhanced Photo Operations" menu.

Thanks, but it looks like that's not supported on G1x and M3 ...
It's a compile time option added relatively recently. AFAIK it's only added to the autobuild for a specific camera when someone requests it and will test the result.
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Offline c_joerg

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Re: How Canon detect an external flash?
« Reply #5 on: 17 / November / 2017, 11:57:43 »
Quote from: waterwingz on 17 / November / 2017, 10:43:22
AFAIK it's only added to the autobuild for a specific camera when someone requests it and will test the result.


I would like to test it once at the G1x (101a) and M3 (101a)  :)

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Offline philmoz

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Re: How Canon detect an external flash?
« Reply #6 on: 17 / November / 2017, 20:42:22 »
Quote from: c_joerg on 17 / November / 2017, 11:57:43
Quote from: waterwingz on 17 / November / 2017, 10:43:22
AFAIK it's only added to the autobuild for a specific camera when someone requests it and will test the result.


I would like to test it once at the G1x (101a) and M3 (101a)  :)


I tested this on my G1X and it works ok. It is enabled on the autobuild for version 1.5 - SVN revision 4928.


Attached is an M3, 1.01a test build.


Phil.

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Offline c_joerg

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Re: How Canon detect an external flash?
« Reply #7 on: 18 / November / 2017, 03:22:40 »
Quote from: philmoz on 17 / November / 2017, 20:42:22
I tested this on my G1X and it works ok. It is enabled on the autobuild for version 1.5 - SVN revision 4928.
Thanks for the quick help …
Quote from: philmoz on 17 / November / 2017, 20:42:22
Attached is an M3, 1.01a test build.

Yes, thanks, works as well.

But there is still a difference between G1x and M3.
G1x Exposure Simulation is switched off when the cam detects an external flash.
The M3 still makes Exposure Simulation off when the cam detects an external flash.

The Problem:
The display of the M3 is black, if I use an external flash with fixed settings in M Mode (1/200s, f5.6, ISO100).
Is there any switch in CHDK which can manipulate the ‘Exposure Simulation’?
Should this work as a work around?
Running the cam in AV Mode and overwriting TV just for the shoot…

Update:
The G1x goes on ‘Exposure Simulation’ when I do the half press :(
« Last Edit: 18 / November / 2017, 05:46:27 by c_joerg »
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