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Sync Multi Cameras - 3d Modeling

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Offline David Ripple

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Re: Sync Multi Cameras - 3d Modeling
« Reply #30 on: 28 / October / 2012, 04:51:13 »
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waterwingz, I greatly appreciate how helpful and quick to respond you are.  Thank you!

I tested 5x Elph100s (the 6th camera arrived in the mail broken).  They all synced at a minimum of 1/30th of a second (based on camera screen refresh).  I still need to set up a more accurate time measurement tool.  However, this is great news, and I will further my tests.
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Offline David Ripple

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Re: Sync Multi Cameras - 3d Modeling
« Reply #31 on: 28 / October / 2012, 11:55:53 »
Currently, I'm triggering the shutter by plugging in and unplugging the power of two daisy chained USB hubs.  The problem is when I leave the Elph100s plugged in and the power connected to the hubs, after about 20 seconds it will automatically trigger the shutter.  This does not happen on the SD800s.  Any ideas how to make it so it does not trigger automatically?
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Offline waterwingz

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Re: Sync Multi Cameras - 3d Modeling
« Reply #32 on: 28 / October / 2012, 12:04:06 »
Quote from: David Ripple on 28 / October / 2012, 11:55:53
Currently, I'm triggering the shutter by plugging in and unplugging the power of two daisy chained USB hubs.  The problem is when I leave the Elph100s plugged in and the power connected to the hubs, after about 20 seconds it will automatically trigger the shutter.  This does not happen on the SD800s.  Any ideas how to make it so it does not trigger automatically?
There is a "hard coded" 20 second timeout in the code for sync mode. 

In sync mode,  if the shutter stays "held" too long (20 seconds) then it gives up on waiting for the sync to complete on the assumption that something is wrong. That was done because the sync loop basically freezes out almost all other camera functionality - making it look like the camera is "dead".

I guess in your case you want to be able to wait longer after setting focus & exposure for the actual event that triggers the shot to occur ?

The SD800's should perform exactly the same way - unless you are running the old 1.0.0 version of CHDK on them.



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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline David Ripple

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Re: Sync Multi Cameras - 3d Modeling
« Reply #33 on: 29 / October / 2012, 04:50:26 »
Yes, It would be great if I could override the hard coded feature.  There will be many times that the model will be trying to strike a certain poses and it takes longer then 20 seconds.  It would be nice to not have to reset the cameras when this happens.
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Offline waterwingz

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Re: Sync Multi Cameras - 3d Modeling
« Reply #34 on: 29 / October / 2012, 10:31:02 »
Quote from: David Ripple on 29 / October / 2012, 04:50:26
Yes, It would be great if I could override the hard coded feature.  There will be many times that the model will be trying to strike a certain poses and it takes longer then 20 seconds.  It would be nice to not have to reset the cameras when this happens.
I rebuilt the old 1.0.0 release and tested the timeout in sync mode.  With that version the timeout existed but rather than being 20 seconds it was only 10 seconds!

We need to think about what to do here.   I guess that I could just eliminate the timeout - not sure if there would be any bad side effects.  I don't really want to add a CHDK menu choice to enable/disable the timeout or set its duration.

« Last Edit: 29 / October / 2012, 10:42:12 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline Microfunguy

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Re: Sync Multi Cameras - 3d Modeling
« Reply #35 on: 29 / October / 2012, 10:54:26 »
Quote from: David Ripple on 28 / October / 2012, 11:55:53
I'm triggering the shutter by plugging in and unplugging the power of two daisy chained USB hubs.  The problem is when I leave the Elph100s plugged in

That is a very curious way of triggering the cameras that is just asking for problems.

It is not recommended for a number of reasons, it is also not necessary.

SDM users of multicam rigs just use a regular USB switch and a number of gentStereo repeaters :-

http://www.gentles.ltd.uk/gentstereo/sdm.htm


David
« Last Edit: 29 / October / 2012, 14:53:47 by Microfunguy »
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Offline waterwingz

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Re: Sync Multi Cameras - 3d Modeling
« Reply #36 on: 29 / October / 2012, 11:01:31 »
Quote from: Microfunguy on 29 / October / 2012, 10:54:26
Quote from: David Ripple on 28 / October / 2012, 11:55:53
I'm triggering the shutter by plugging in and unplugging the power of two daisy chained USB hubs.  The problem is when I leave the Elph100s plugged in
that is a very curious way of triggering the cameras that is just asking for problems.
Now that you mention it, I was wondering about that too. You would really need to look at the waveform of how the power decays using an oscilloscope on the USB line to the camera to determine if you are getting a sharp cut-off or a slow decay. The later case will surely cause variations in sync quality.

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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline Microfunguy

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Re: Sync Multi Cameras - 3d Modeling
« Reply #37 on: 29 / October / 2012, 11:39:39 »
Quote from: David Ripple on 28 / October / 2012, 04:51:13
I still need to set up a more accurate time measurement tool. 

You will have to point all five cameras at a CRT.

By definition, multicam rigs cannot provide precision synch.

For example, with the S95 75% of shots with TWO cameras have a synch difference of one msec or less.
However, 25% have errors a lot more than that up to 8 msec.
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Offline David Ripple

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Re: Sync Multi Cameras - 3d Modeling
« Reply #38 on: 30 / October / 2012, 23:14:25 »
I bought the Gentles solution and used it last night for the first time.  For my purpose, and with only 5 cameras both gentles and USD daisy chain provide the same result.  Keep in mind with 3d modeling software, I need probably only about 10 msec accuracy.

The gentles is nice because of the easy shutter button. Also, I think as I add cameras it should be better with the power decay.  But the only way to know is to test it.  Or if someone else has done the test.

The USB daisy chain seems to be better when it comes to all the cameras always taking the picture.  In my limited tests with Gentles I found that sometimes if I hit the shutter button at different time intervals, some of the cameras activate the shutter and some do not.  I also noticed that sometimes after triggering the shutter at odd time intervals.  i.e.  shoot, wait 12 seconds - shoot, wait 5 seconds - shoot, wait 2 second - shoot, etc. it makes the shutter speed setting messed up.  Meaning, I can no longer set the shutter to 1/30.  It does not even have that option in the menu.  I have to restart the camera a couple times or re-install the CCHDK2.CFG file in order to have all the shutter speed options again.  Having all the cameras always shot the same amount of pictures is very important for my naming convention.  Any insight into this would be appreciated.

waterwingz - maybe it would be good to make the timeout 2 minutes.
« Last Edit: 30 / October / 2012, 23:21:38 by David Ripple »
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Offline waterwingz

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Re: Sync Multi Cameras - 3d Modeling
« Reply #39 on: 30 / October / 2012, 23:28:54 »
Quote from: David Ripple on 30 / October / 2012, 23:14:25
I bought the Gentles solution a couple weeks ago and received it several days ago and used it last night.  For my purpose, and with only 5 cameras both gentles and USD daisy chain provide the same result
So far, so good.

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The gentles is nice because of the easy shutter button. Also, I think as I add cameras it should be better with the power decay.  But the only way to know is to test it.  Or if someone else has done the test.
If they did, they have not posted it.  Far too common a human failing once one has the answer I fear.  Let us know what you find out please ?


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The USB daisy chain seems to be better when it comes to all the cameras always taking the picture. 
Okay .. well that's strange.

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In my limited tests with Gentles I found that sometimes if I hit the shutter button at different time intervals, some of the cameras activate the shutter and some do not. 
Hmmm ..  you have all of them setup as "one press" and "normal" ?  And do they all go into "waiting for sync" mode when you press the button  (lcd off and sync led lit) before you release USB power ? If they all do not go there then that is very strange.

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I also noticed that sometimes after triggering the shutter at odd time intervals.  i.e.  shoot, wait 12 seconds - shoot, wait 5 seconds - shoot, wait 2 second - shoot, etc. it makes the shutter speed setting messed up.  Meaning, I can no longer set the shutter to 1/30.  It does not even have that option in the menu.
Trying to follow you here - its just not possible for the USB remote to change that sort of thing.  Are you telling me that if you go to the CHDK "Extra Photo Operations" menu then the "Override Shutter Speed" menu item is not there ?????

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I have to restart the camera a couple times or re-install the CCHDK2.CFG file in order to have all the shutter speed options again. 
So multiple resets fixes it ?   
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Ported :   A1200    SD940   G10    Powershot N    G16
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