Sync Multi Cameras - 3d Modeling - page 7 - General Discussion and Assistance - CHDK Forum
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Sync Multi Cameras - 3d Modeling

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Offline waterwingz

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Re: Sync Multi Cameras - 3d Modeling
« Reply #60 on: 07 / December / 2014, 10:16:53 »
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Quote from: andrew.stephens.754365 on 07 / December / 2014, 06:44:10
What could explain this?
I misunderstood your question. 

The code followed in both cases is the same and the effect of the misplaced "hook" is the same as not having sync enable at all.  My response  was intended to convey the information that the sync error between cameras would be the same in either situation (as sync error between cameras had been the topic if most of the previous part of the thread).

However with one-push,  when sync is enabled, that process starts when the USB=5V is asserted.  When sync is not enable, the process starts when USB goes back to 0V.   Just like your chart shows.

(I can't follow the process of your two-step sequence.  Steps 5&6 only open the switch. There seems to be no point at which you close the switch)
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline andrew.stephens.754365

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Re: Sync Multi Cameras - 3d Modeling
« Reply #61 on: 07 / December / 2014, 10:33:50 »
Understood - thanks.

Corrected chart attached (for the record).
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Offline waterwingz

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Re: Sync Multi Cameras - 3d Modeling
« Reply #62 on: 07 / December / 2014, 11:00:42 »
Quote from: andrew.stephens.754365 on 07 / December / 2014, 10:33:50
Corrected chart attached (for the record).
That's better.

Here's a little background about the "one push" behavior. The reason for that action is that using sync requires two different user initiated actions or events.   The first action starts the shooting sequence - which then runs until it hits the "sync hook" and waits there.  The second action releases the shooting sequence from the "sync hook" wait.   

With a "one press" setup,  the code needs to use the 0v->5v transition to start the sequence and the 5v->0v to finish it.   In non-sync situations,  "one press" does a shutter half-press on 0->5 and shutter full-press on 5-0.   Thus, in sync mode, there is nowhere to put the half-press and it is sacrificed to allow the two necessary action for sync.

Two push does not have the same limitation so sync in that mode functions the same as no-sync. But it has the added advantage of a "cancel' mode, which happens if you don't do the second push within 1/2 second of releasing the first push.  Just as your chart shows.
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline andrew.stephens.754365

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Re: Sync Multi Cameras - 3d Modeling
« Reply #63 on: 07 / December / 2014, 20:01:30 »
Quote from: waterwingz on 07 / December / 2014, 11:00:42
Thus, in sync mode, there is nowhere to put the half-press and it is sacrificed to allow the two necessary action for sync.

I hadn't thought about that - useful information. Does this mean that chdk overrides are still applied but autofocus loses any meaning ?

Attached is a spreadsheet with 3 possible timings for two stage capture on two separate groups of cams (using A1200 timings as a potential baseline here http://chdk.setepontos.com/index.php?topic=8312.msg107601#msg107601

A:
(i) Synch hook missing (ii) Onespush (iii) Synch  Enabled. Manual Focus / Manual Mode, no chdk overrides - long canon shutter period. Two stage flash capture requiring total of 64ms blackroom conditions.

B:
(i) Synch hook missing (ii) Onespush (iii) Synch  Enabled. Manual Focus / Manual Mode, no chdk overrides - canon shutter period, say 10ms. Continuous light for first group cature. This then moderated to allow projector "noise" pattern through. Total period: first shutter/sensor open -> last shutter/sensor closed = 75ms

C:
(i) Synch hook fixed (ii) Onespush (iii) Synch  Enabled. Manual Focus / Manual Mode, no chdk overrides - canon shutter period, say 10ms. Continuous light for first group cature. This then moderated to allow projector "noise" pattern through. Total period: first shutter/sensor open -> last shutter/sensor closed = 69ms

However, it may be that precision synch could provide far superior results (and the outliers be ignored perhaps) - it would therefore still be appreciated if the synch hook could be enabled for the sx150is at some stage (and whatever else is/(may be) needed to enable precision synch).
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