Re: [photo-3d] Digest Number 65

[Brian Reynolds <reynolds@xxxxxxxxx>]

Olivier Cahen wrote:
> Brian Reynolds, in Photo-3d@xxxxxxxxxxx, Digest 65, message 11, wrote :
> > That's more a circuit problem than an oscilloscope problem.  You need
> > to design the circuit so that you can tell which photo transistor is
> > on without needing mutilple inputs on hte oscilloscope.  One way to do
> > this is by adding resistors to the circuit as a voltage divider.
> > 
> > Radio Shack has a series of very useful circuit booklets written by
> > Forest Mims III.  They're fairly small and printed on graph paper.
> > There is probably one on using light sensors that would have a useful
> > circuit.
> >
> Hello. I do not understand why you need such a sophisticated
> equipment.  I already answered this question in a short response to
> Allan Griffin in the last December issue of "Stereoscopy", you could
> easily find it even if you are not yet a member of the ISU.
>
> Allan talked about using a professional oscilloscope, and did not
> know how to find one and how to use it.
>

The original question asked how to use an analog oscilloscope to check
shutter synchronization.  Since Alan has an oscilloscope and had
already been tinkering with it I figured I'd point out an avenue of
research for him.

By the way, anyone with a computer, an audio capture card, a couple of
dollars of electronics parts and some audio capture software can use
their computer as a (very) low end digital oscilloscope.  A Deja news
search for "shutter test sound card" in rec.photo.* should turn up
some information.  Of particular interest are
<URL:http://www.geocities.com/Yosemite/2131/shspeed.html> and
<URL:http://www.smu.edu/~rmonagha/mf/shutterspeed.html>.

> Simply use your home oscilloscope, I mean your TV set, take a
> picture of the same TV image with your two cameras, you will esaily
> measure the difference of exposure times and the time lag between
> your camera shutters, with a precision better than a
> milliseconds. No need to understand electronic circuitry for that.
>

The TV method will tell you about shutter speeds and synchronization
(if you take both frames at the same time using whatever method you
plan to use in the final setup), but requires that you count video
lines on the film while using magnification.  This is less convenient
than using the oscilloscope that Alan already has.

-- 
Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
reynolds@xxxxxxxxx              | "Oooh!"
http://www.panix.com/~reynolds  |    -- Dexter and Dee Dee
NAR# 54438                      |       "Dexter's Laboratory"

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