Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

negnet

« on: 13 / September / 2016, 06:59:08 »

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Hi!
I am using Canon IXUS160 camera with external flash Youngnuo speedlight YN560 IV.
I need to get continuous shooting as fast as possible with flash (I am using scripts to get it).
As far as IXUS160 flash brightness and battery are limited I am using an external flash in slave mode to sinc with IXUS160.

Using CHDK I set flash power of the IXUS160 to minimum (and flash always on), therefore IXUS160 could shoot with flash with increased speed. IXUS160 require up to 5 sec to recharge the capacitor and then it is able for the next shoot. 5 sec is OK for me. External flash are able to recharge in 5 sec and flash again. So everything is fine for now.

But after 20th shoot IXUS160 start to require much more than 5 sec to be able to shoot again with minimum flash power (up to 20-30 sec). I changed flash power from min to max and again 20 shoots are the limit. It is the same on fully charged battery and almost discharged battery. I also tried it without CHDK - again 20 shoots and no more.
Looks like it is the IXUS160 firmware limit.

The only thing that helps is rebooting! But rebooting is very inconvenient for me.

Are there the other ways how to extend the number of 20 shoots with flash on IXUS160?

I need your help
Many thanks in advance
Negvet

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srsa_4c

4450

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #1 on: 13 / September / 2016, 14:37:12 »

That limit is likely there to prevent overheating in parts of the flash circuit.

If you'd like to try breaking your camera, you can use
poke(0x464C, 20) (ixus160 100a only, 0x4614 + 0x38)
to reset the counter. The equivalent method is working on my a3200.

The variable can be found right after the CreateTask call that starts task_EFChargeT, it is set to its initial value (20) there. It can't be set to a higher value because the firmware ignores larger values.

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negnet

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #2 on: 19 / September / 2016, 08:48:29 »

Thanks for the answer, srsa_4c!

I will definitely try your solution.
I would like to exclude the internal flash to trigger the external one but I do not know how.. I tried to sense the LED on the camera and then trigger the external flash with arduino, but it did not work (led always flash different time, although i command it to flash a certain time, it varies for several milliseconds). I need the shortest possible exposure time - 0.0005 and my external flash duration is 0.079 ms. That is why several milliseconds is a big mismatch for me.

May be I could save the camera (with extended number of internal flashes) by reducing the power of the internal flash. CHDK provides three options: high, mid and low power of internal flash. How is it possible to reduce the power of the min option? I believe that if I will redirect the light from the internal to the external flash with something (like optical fiber), it will be enough light to trigger the external flash.

Thanks!

« Last Edit: 19 / September / 2016, 09:00:56 by negnet »

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srsa_4c

4450

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #3 on: 19 / September / 2016, 17:00:37 »

Quote from: negnet on 19 / September / 2016, 08:48:29

May be I could save the camera (with extended number of internal flashes) by reducing the power of the internal flash. CHDK provides three options: high, mid and low power of internal flash. How is it possible to reduce the power of the min option?

To answer this one: the 3 levels are actually provided by the Canon firmware - CHDK just makes them available as is.

About the LED: it might be possible to achieve higher accuracy, but I've never experimented with that. See http://chdk.wikia.com/wiki/Script_Shooting_Hooks , hook_shoot.

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reyalp

13718

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #4 on: 19 / September / 2016, 17:18:05 »

Quote from: srsa_4c on 19 / September / 2016, 17:00:37

About the LED: it might be possible to achieve higher accuracy, but I've never experimented with that. See http://chdk.wikia.com/wiki/Script_Shooting_Hooks , hook_shoot.

Unfortunately, I doubt this will provide the kind of precision negnet is looking for, there's ~10ms uncertainty just in the synchronization between script and capt_seq, and potentially more between the remote hook and the shot starting.

Sub-ms precision would probably require hooking the actual code that fires the canon flash or starts the exposure, in C or ASM code.

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negnet

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #5 on: 20 / September / 2016, 04:09:01 »

Thanks for your answers!

Quote from: reyalp on 19 / September / 2016, 17:18:05

Sub-ms precision would probably require hooking the actual code that fires the canon flash or starts the exposure, in C or ASM code.

I am not sure if I know where to start with this.. Any starting points?

But may be the other way is easier, if I know a man who are familiar with electronics a bit. I know there have to be the busline that goes out from the shutter. One of the connections of this busline have to carry the signal that inform about the opened shutter (I guess there are electronic connectors, that connect with each other when the shutter is opened, producing the signal that goes to the flash and probably other places).
What if I try to find this busline and nessesary connector and assemble the circuit that trigger the external flash based on the signal that goes through this connector? Anybody tried this?
Basically waterwings suggested something similar here:

Quote from: waterwingz on 14 / November / 2015, 15:52:08

... you probably would want to work your way back into the circuit and find the signal used to fire the thrystor that triggers the flash tube. But you really need to know a lot about electronics and circuit design, coupled with some reverse engineering experience before you try something like that. Even the little flash circuit in a Powershot camera has enough energy to knock you flat on your posterior if you do something wrong.

I just did not find if someone reported about usage of this approach.

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reyalp

13718

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #6 on: 20 / September / 2016, 13:20:53 »

Quote from: negnet on 20 / September / 2016, 04:09:01

I am not sure if I know where to start with this.. Any starting points?

Not really, I haven't investigated this code specifically.

The related tasks CHDK currently hooks are CaptSeq and on some cameras ExpDrv and DvlpSeq. I don't think either of these directly starts the image exposure. CaptSeq probably tells another task to do it with a message or event flag, somewhere between where the remote hook and raw hook are called.

If you want to look for how the normal flash is triggered, related code often refers to strings containing "EF" (for "electronic flash", AFAIK)

You would need to be familiar with reverse engineering and ASM code to have much chance of success with this approach.

Quote

But may be the other way is easier, if I know a man who are familiar with electronics a bit. I know there have to be the busline that goes out from the shutter. One of the connections of this busline have to carry the signal that inform about the opened shutter

The mechanical shutter on these cameras is generally only used at the end of the exposure, to cover the sensor during readout. AFAIK the exposure is started electronically, with the shutter already open.

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negnet

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #7 on: 21 / September / 2016, 08:49:00 »

Quote from: reyalp on 20 / September / 2016, 13:20:53

You would need to be familiar with reverse engineering and ASM code to have much chance of success with this approach.
The mechanical shutter on these cameras is generally only used at the end of the exposure, to cover the sensor during readout. AFAIK the exposure is started electronically, with the shutter already open.

reyalp, thanks for this info. looks like it is really not that easy.

srsa_4c, I tried to reset the number of maximum shoots with flash according to

Quote from: srsa_4c on 13 / September / 2016, 14:37:12

If you'd like to try breaking your camera, you can use
poke(0x464C, 20) (ixus160 100a only, 0x4614 + 0x38)

but it did not work. I have a lua script with the following line: "poke(0x464C, 25)".
I upload and run this script on ixus 160 and then trying to shoot continuously. I am using python for this:
os.system(""" ptpcam --chdk="upload reset_flash.lua A/CHDK/SCRIPTS/reset_flash.lua" """)
sleep(1)
os.system(""" ptpcam --chdk="lua require('lptpgui').exec_luafile([[A/CHDK/SCRIPTS/reset_flash.lua]])" """)
sleep(1)
shooting with for loop...

But it again stop to shoot after the 20th shoot. What am I doing wrong here?

Thanks!

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srsa_4c

4450

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #8 on: 21 / September / 2016, 11:04:32 »

Quote from: negnet on 21 / September / 2016, 08:49:00

But it again stop to shoot after the 20th shoot. What am I doing wrong here?

The poke instruction has no permanent effect, it only resets the flash counter. Execute it once after 18 shots. 18, because re-setting it to 20 results in less than 20 shots with flash.

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negnet

Re: Continuous shooting with flash limited at up to 20 shoots!? IXUS 160

« Reply #9 on: 22 / September / 2016, 10:00:39 »

srsa_4c, many thanks!

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