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

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

----- Original Message -----
From: "David W. Kesner" <drdave@xxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxxxxxx>
Sent: Wednesday, February 14, 2001 6:19 AM
Subject: Re: [photo-3d] The Stereoscopic Society Annual Competitrion


> 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. I didn't try any
> formulas - those are just for math geeks and those without a
> dedicated macro stereo camera *{;-)
>
> Could someone with access to these formulas tell me what the
> maximum distance you could achieve between near and far points
> with a stereobase of say 11mm? We are also talking about a
> macro shot, so maybe a 100mm lens and inches to the subject.
>
> Thanks,
>
> David W. Kesner
> Boise, Idaho, USA
> drdave@xxxxxxxxxx


This is an excellent picture, and a very good example of what can be done
with macro stereo images.

Stereo photographers often avoid macro because it is perceived as difficult,
with a lot of math, etc.  Actually, very good macro stereo images can often
be made with only a little logic, and no calculations.

Basically, the two main ways for minimizing parallax differences over long
distances are to either use short focal length (wide angle) lenses, or a
narrow stereo base, or both.   The wide angle lenses also increase the
apparent depth of field, an advantage in macro work.

Still life images such as this example can be made with a conventional
non-stereo camera using slide-bar techniques.  If a reflex camera is used,
the technique is to compare similar parts of near and far objects in one
view to how much difference there is in the viewfinder from the other view.
Looking through the viewfinder while moving the camera makes this quite
apparent.  Then use your experience to judge the best position.  This
experience can be gained through practice, by "bracketing" positions the
first few times it is done.

Contrary to popular opinion, a narrow stereo base does not necessarily mean
reduced stereo relief.  The total depth range in the scene (nearest point to
farthest point) determines this.  Often excessive depth is more of a problem
than getting enough.  Macros, correctly done, often have more depth range
than conventional subjects.  I would encourage everyone to experiment with
this fascinating area.

JR

>
>