Re: [photo-3d] Re: Testing synch of twin cameras

["Alan Lewis" <3-d@xxxxxxxx>]

--- In photo-3d@xxxxxxxxxxx, Brian Reynolds <reynolds@xxxx> wrote:
> > Following up on the thread about how to verify the actual synch of
> > twin camera shutters:
> This is a pair of photo transistors in series.  It is the equivalent
> of a logical AND.  You will only get a signal when light strikes 
both
> T1 AND T2.  This will tell you the amount of overlap between the
> shutter firings, but not whether the shutters are in sync.  Looking
> carefully at the diagrams above you'll notice that both transistors
> fire for the same amount of time, but offset by one time tick.  The
> output shows only the overlap of the two signals.

Yes, that's what I was thinking.  I figured that if you knew the 
individual shutter speeds of each shutter then the best synch you 
could measure with this setup was a signal equalling the fastest 
shutter speed.  You would be synch'd at least within the difference 
between the two shutter speeds, which should be darn good.
If you had no signal then the shutters were completely un-synch'd. 
The signal would gradually increase to an ideal value equalling the 
fastest shutter speed as they were adjustedfor better synch.

> 
> > If the scope was able to take two signals then the transistors 
could
> > be in parallel and the two shutters could be superimposed over 
each
> > other.
> > 
> 
> This should work, but I'm not quite sure that I understand what you
> mean by "If the scope was able to take two signals".  

What I really meant is that I haven't figured out how to use my 
analog scope.  I really don't know anything about oscilloscopes but 
am trying to learn.  As is usual with stereo photography, you have to 
learn a lot of other seemingly unrelated disciplines to accomplish a 
task.  I haven't mastered the oscilloscope yet.
I've figured out the stereoscope, but not the oscilloscope.

If this thread keeps going maybe I'd better take it to Tech 3-d.  I 
probably should have put it there anyway.

Alan Lewis
3-d@xxxxxxxx


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