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multiple camera sync

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Offline colombo11

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Re: multiple camera sync
« Reply #10 on: 09 / February / 2013, 17:07:36 »
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those sync time mentioned are they enough fore a good time slice effect?

why cameras introduced in and after 2011 have poor synch isn't it suppose to be the other way around? (maybe canon does this on purpose?)
and is that problem applied also if i use  the other way i mentioned before for sync triggering http://imgur.com/a/i45Qv#0 (if not on canon's cameras maybe on some other brands)

Any way let me remind you of a project with an sx camera :
http://www.martin-hoppe.com/indexMAIN.html
http://www.frozen-time-cam.com/
that is sync enough for me!! it looks  perfect. i will be more then happy whit that result.
i believe it was sx200 X 50 on chdk. ((is that model is exceptional for the sx series?)) it's even looks taken with a high shutter speed
 (if anybody knows what was the sync time in that project please post it)
i need a camera with about the quality of the sx 220/230 and in the same price range which is capable for good sync results...

 i am taring to avoid a stupid mistake like buying the wrong camera

« Last Edit: 09 / February / 2013, 17:52:16 by colombo11 »
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Offline waterwingz

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Re: multiple camera sync
« Reply #11 on: 09 / February / 2013, 17:58:24 »
Quote from: colombo11 on 09 / February / 2013, 17:07:36
thous sync time mentioned are they enough fore a good time slice effect?
I don't know if there is an expert on "bullet time" on this forum so I'm not sure you will get a good answer.  I googled time slice and found its often called bullet time.  Interesting stuff but I couldn't find any specs on how good the sync needs to be.   With CHDK & SDM,  stereo photography requires really precise sync to create a credible 3D illusion as your eye will detect even small changes due to something moving and reject the 3D effect.   Looking at your examples I tend to suspect that the sync requirements are much less that for 3D.

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why cameras introduced in and after 2011 have poor synch isn't it suppose to be the other way around? (maybe canon does this on purpose?)
Sync is a something CHDK adds to the Canon firmware.  Canon knows nothing about it.  It became more difficult after 2011 because the software in the cameras changed enough that the implementation of CHDK that worked well in older cameras no longer worked well in newer cameras.  A new hack method is needed and some work has been done on that but there is no general solution yet.

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and is that problem applied also if i use  the other way i mentioned before for sync triggering http://imgur.com/a/i45Qv#0 (if not on canon's cameras maybe on some other brands)
Are you going to keep asking that question in the hope I will change my answer ?

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that is sync enough for me!! it looks  perfect. i will be more then happy whit that result.
i believe it was sx200 X 50 on chdk. ((is that model is exceptional for the sx series?)) it's even looks taken with a high shutter speed (if anybody knows what was the sync time in that project please post it)
i need a camera with about the quality of the sx 220/230 and in the same price range which is capable for good sync results...  I am trying to avoid a stupid mistake like buying the wrong camera
If it was an sx200 then it would likely have better sync than an sx220/230.  The only person I remember posting on doing this sort of thing was Alarik but I don't believe he defined how good the sync needed to be in these forum threads :


http://chdk.setepontos.com/index.php?topic=8312.0
http://chdk.setepontos.com/index.php?topic=8273.0
http://chdk.setepontos.com/index.php?topic=8305.0 ( he was having s/w problems with the sx130 !)

You could try sending him a personal message ?

You might also want to read through this :  http://forum.chdk-treff.de/viewtopic.php?f=20&t=2037   I'd suggest using Google's Chrome browser as it will automatically translate it for you from German.
« Last Edit: 09 / February / 2013, 18:17:59 by waterwingz »
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Offline andrew.stephens.754365

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Re: multiple camera sync
« Reply #12 on: 20 / March / 2013, 12:33:57 »
Hi, i'm new here and extremely naieve to all matters photography / photogrammetry / cdhk, so please be kind :'(.

I have been reading the forum as much as I can over the last couple of days including briefly:-
Topic: testing sync among more camera -
http://chdk.setepontos.com/index.php?topic=8312.0 and ,
Topic: Sync Multiple Cameras -
http://chdk.setepontos.com/index.php?topic=7758.0  - [who apparently implemented a 28 cam SD1300 photogrammetry SDM solution]
and "reyalp's wonderful Topic: alternative ptp client
http://chdk.setepontos.com/index.php?topic=6231.0

Now my problems are many - including  not being overly technically minded and having a pretty poor memory. So, while I do not think cdhk can help i'm not sure - so i'll continue in the hope of gaining a little [lot ;)] more understanding.

Prior to realising I am not a millionaire the plan was to purchase (i)70x600D's (ii) multi-studio flash (iii) arduino controlled commercial "chainable" opto-isolator shutter/flash controller (iv) commercial usb tether software - this being limited to around 16 cam control per PC but networkable so all frames can be centrally gathered and processed into a 3D mesh.

DSLR Process workflow: In normal ambient room lighting my subject [human/pet] would pose, the tether software would be used to (a) autofocus and (b) set exposure to 4ms. Autofocus would then be turned off. The room lights would be turned off - an ambient room light sensor attached to the arduino controller would cause trigger shutters open [via opto-isolators to 2.5mm jacks], all shutters would be open at [latest] after 72ms, the flash would fire [via arduino controller] at 73ms [for 100microsec] and the last shutter would be closed at 76ms. Room lights turned back on after a tenth of a second and the baby or pet dog would never know it had been dark or blinked an eye !     

All good, apart from the budget ! hence this post with point&shoot...please remember i'm just making this up as I go along, so logic may be very low...

Point&Shoot Scenario:
turn room lights out at time=>0, then:
If it takes a human, say, 300ms [30hundredths, 3tenths] to blink, then Microfungy's earlier post leads me to think that chdk usb remote shutter release may get the "shutters" [if that's the right term on a point&shoot], OF SAY 100 CAMERAS !, all open , within a "small number" of hundredths [let's say 10hundredths maximum] ? of each other.

Query1: might anyone comment on the delay between the usb line going to 0V and the shutter of the first camera to be open ? [USB powered mult-hub network]

Now, if that delay was, say, 5 hundredths maximum [??] then I could [somehow ??] wire the arduino ambient light-sensor / studio flash controller to trigger the 100microsec flash at a fixed time=> 10hundredths + 5hundredths + 2 hundredths padding  = 17hundredths
ALSO
please bear in mind that the plan is to use one superduper PC [multi PCI USB3.0 host controllers ?] and therefore a number of levels of powered USB hubs between camera and PC
AND
hoping that I have not misunderstood "waterwingz" note about the "mechanical" switch, that I further hope can be made electronic and also interface to the arduino flash controller [not much to ask or decipher  ??? what an awful first post !]

Query2: Before the room lights are turned off I need to "prefocus" then "lock the focus". I've no idea (a) if that can normally happen on a point&shoot (b) if chdk can help it happen (c) if chdk can help it happen then can it happen in combination with my Query1 and lead to successful frame capture, in say 50 hundredths exposure time and 100microsec flash capture.

Ok, the exposure time needs to go up quite a bit, the ambient room lights need to stay off a while longer and the 3D mesh will not be that with a network of DSLR's but, if I could get this to work, I could maybe still buy some food to eat  :haha 

Here's hoping ! - any comments from anyone [but especially the "guru genuises" welcome, even if that should be just "wise-up... :) ahggg, just pressed "post", hope this is not too embarassing...

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Offline waterwingz

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Re: multiple camera sync
« Reply #13 on: 20 / March / 2013, 12:55:25 »
I'll kick this off but I'm sure there will be several opinions on this.

Quote from: andrew.stephens.754365 on 20 / March / 2013, 12:33:57
If it takes a human, say, 300ms [30hundredths, 3tenths] to blink, then Microfungy's earlier post leads me to think that chdk usb remote shutter release may get the "shutters" [if that's the right term on a point&shoot], OF SAY 100 CAMERAS !, all open , within a "small number" of hundredths [let's say 10hundredths maximum] ? of each other.
Somewhat dependent on the camera you pick but I believe you have a pretty good chance of this working if a 10 mSec difference from the first camera to the last camera is acceptable.

The question to ask is what happens if you occasionally don't get all the camera's sync'd.   Is the subject matter a "one time only" event or can you shoot multiple times to make sure its right?

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Query1: might anyone comment on the delay between the usb line going to 0V and the shutter of the first camera to be open ? [USB powered mult-hub network]
You might have to experiment a bit to calibrate this but it should be do-able. Most of the data you have seen compares differences between the  same model of camera - not the time between USB going to zero and the shutter opening.

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please bear in mind that the plan is to use one superduper PC [multi PCI USB3.0 host controllers ?] and therefore a number of levels of powered USB hubs between camera and PC
Are you going to try and trigger with PTP ? If you plan to use the USB remote functionality in CHDK then you need a way to switch the 5V power - not the USB data pins.  This is not a standard feature on a PC's USB port.

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Query2: Before the room lights are turned off I need to "prefocus" then "lock the focus". I've no idea (a) if that can normally happen on a point&shoot (b) if chdk can help it happen (c) if chdk can help it happen then can it happen in combination with my Query1 and lead to successful frame capture, in say 50 hundredths exposure time and 100microsec flash capture.
Unless I'm missing something here,  this should be easy to do with a simple Lua or uBASIC script.
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Offline Microfunguy

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Re: multiple camera sync
« Reply #14 on: 20 / March / 2013, 13:23:25 »
First of all, let us get real.

How much money do you have available ?

Even the cheapest option is not going to be 'cheap'.

David
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Offline lapser

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Re: multiple camera sync
« Reply #15 on: 20 / March / 2013, 14:01:39 »
This is way out of the box, but has anyone experimented with how fast the live view sensor works? That is, can you watch the live view until you see the flash, and start your sync from there? If so, it could all be done in software.

The motion detect code does something like this. How fast does it respond to movement?
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Offline Microfunguy

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Re: multiple camera sync
« Reply #16 on: 20 / March / 2013, 14:14:13 »
Quote from: lapser on 20 / March / 2013, 14:01:39
can you watch the live view until you see the flash

You will not see the flash (on the screen) in Live view.
When the flash occurs the sensor is already capturing data.

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The motion detect code does something like this. How fast does it respond to movement?

I don't know the CHDK figures but many tens of milliseconds.

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Offline andrew.stephens.754365

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Re: multiple camera sync
« Reply #17 on: 20 / March / 2013, 14:31:42 »
Quote from: Microfunguy on 20 / March / 2013, 13:23:25
First of all, let us get real.

How much money do you have available ?

Even the cheapest option is not going to be 'cheap'.

David

Just about as real as I can get Microfungy,

[very] Low 10's of thousands, including a beast of a pc - I only became aware of photogrammetry after Christmas past. I bought 4 canon dslr off gumtree before doing a budget and I still haven't re-opened those boxes. I hate to say it but the only camera I know how to [sort of] use is on my mobile phone.

The DSLR route is proven - if I can figure some way to mix DSLR / point&shoot solutionit'd be ideal. Only thought a little about that but not much yet.

If the idea does well [and a mixed solution is possible] i'll swap out point&shoot to DSLR as any money comes in...yeah, it's a big deal dor me.

I know it's a long way oiut of the box but ingenuity can sometimes go a long way...I have a [very little] procedural programing knowledge [MS Office VBA :(] and a degree in electronics 25 years ago so might be able to stick with a little tech jargon.  :o
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Offline Microfunguy

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Re: multiple camera sync
« Reply #18 on: 20 / March / 2013, 14:41:51 »
That is a lot of money.
There are members on the Yahoo SDM Group who can give you practical advice regarding multicamera rigs.
Why do you need so many cameras ?

If you will settle for point-and-shoot cameras we can recommend some very inexpensive ones with remarkable synch.

However, what value would the maximum mis-synch need to be ?

That will affect the camera recommendation.
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Offline lapser

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Re: multiple camera sync
« Reply #19 on: 20 / March / 2013, 16:08:28 »
I have an idea how to do this with the time lapse routines I've already written. There are no connections between the cameras required. That is, no usb cables .

My time lapse program works in continuous mode by delaying in capt_seq_hook_set_nr() right before the shutter opens. (This is about where the USB sync hooks in time wise too.) This way, the time between shutter opens is very precise.

I've run time lapses with 2 cameras next to each other so I can hear the shutters on both cameras clicking. The pattern of clicks stays the same for hours. So with an interval set to 1000 msec, all cameras are taking pictures precisely 1000 msec from the last picture.

If you put the cameras in a dark room with a strobe flashing at precisely 1000 msec intervals, you can get all cameras to sync up to the strobe fairly quickly. I also have a shot meter routine that measures the brightness of the shot from the raw buffer. You could set the interval to 990 msec and wait until the brightness suddenly increased when the shutter was open during the flash. You could adjust the shutter speed to sync a little faster, and even find the minimum shutter open time that could reliably capture the flash.

Each camera would signal that it was in sync, maybe by turning off its backlight. The cameras would all keep taking shots in sync as long as you wanted.

As I said, it's out of the box, but opens up some new possibilities. Time slice time lapse anyone?

Here's a few time lapse examples:

http://www.youtube.com/watch?v=b_nVZbV-MR4#ws

http://www.youtube.com/watch?v=uRio1KM-LuM#ws
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