Re: [photo-3d] The Stereoscopic Society Annual Competitrion

["Don Lopp" <dlopp@xxxxxxxxxxxxxxx>]

It might help if we were told the focal length of the lens used DON
----- Original Message -----
From: "John A. Rupkalvis" <stereoscope@earthlink.net>
To: <photo-3d@yahoogroups.com>
Sent: Wednesday, February 14, 2001 10:22 PM
Subject: Re: [photo-3d] The Stereoscopic Society Annual Competitrion


>
> ----- Original Message -----
> From: "William Gartin" <william_gartin@mac.com>
> To: <photo-3d@yahoogroups.com>
> Sent: Wednesday, February 14, 2001 9:07 PM
> Subject: Re: [photo-3d] The Stereoscopic Society Annual Competitrion
>
>
> > on 2/14/01 12:07 PM, Paul Talbot wrote:
> >
> > > "David W. Kesner" wrote:
> > >>
> > >> Paul Talbot writes:
> > >>
> > >>> My WAG: he used a
> > >>> very small stereo base.  But I have no macro experience and
> > >>> you do, so I presume you can't make the math work with the
> > >>> MAOFD formulas, right?
> > >>
> > >> I have no idea what the stereobase was on this image, but it
> > >> was large enough to achieve good stereo.
> > >
> > > My guess: only a very small stereo base is needed when there is
> > > something that close to the camera and the scene extends a long
> > > way.
> > >
> > > Paul
> > >
> > >
> > >
> > What would be considered an appropriate separation angle in degrees? If
> you
> > know that, then all you should need is the distance to the subject to
find
> > the appropriate separation, right?
> >  --
> > William Gartin <william_gartin@mac.com>
>
>
> No.  The optimum separation angle (and the resulting parallax) are
variables
> that cannot be quantified for all subjects.  Each subject is different,
and
> several factors enter into the judgment as to what is best for a specific
> stereo image.  Things such as contrast, color, association, sharpness,
> relationship of other objects in the image, etc., etc., all must be
> considered in the evaluation of the most appropriate settings.  Even
whether
> convergence is parallel (shift lenses or shift mounts) or toed in.
>
> You must consider that the eye/brain system does not instantly take in an
> entire image simultaneously, but rather "scans" the image.  If an object
has
> nothing between it and the background, much narrower parallaxes are
required
> than if there are objects in between.  With intermediate depth references,
> the eyes can track from one object to another, rather than "jumping"
> directly between foreground and background, thus permitting wider parallax
> differentiation between the nearest and farthest points in the image.
>
> I use an extreme example to illustrate this.  It is possible to "create"
an
> image such that nothing is changed except the subject, and in one instance
> it will work, and in the other not.
>
> An actor is standing in the foreground, say about two meters from the
camera
> (Stereo Realist, dual cameras, whatever).  The scene is in the Mojave
> Desert, with nothing else in the picture except the mountains on the
> horizon, several miles away.
>
> Regardless of where the cameras are converged, it will not be possible to
> view the image without severe eyestrain, and a "splitting" of either the
> image of the mountains, or the image of the actor (depending upon which
you
> concentrate on).
>
> Then, do not move the camera or make any changes to your photographic
> procedure.  Simply add another object (a prop such as an artificial cactus
> will do nicely, or just drive an automobile into the scene).  This
> "reference" object should be about four meters from the camera.
>
> Now, the image will be much easier to view.   Same close point and far
point
> parallaxes, everything else the same.   Stereoscopic imaging is extremely
> subjective.
>
> Many people have spent a lot of time creating mathematical tables.  For
the
> most part, these are most useful for the designers of cameras and other
> imaging equipment.  The stereo photographer would be far better off
spending
> that time in making pictures and learning by experience what factors
affect
> the optimum images under what combination of circumstances.  Visual
> viewfinding systems (reflex cameras, video camera or camcorder
viewscreens,
> etc.), as well as studying the resulting images, can be very educational.
>
> JR
>
>
>
>
>