[MF3D.FORUM:812] Re: I need a MF 3D Dr.

["don lopp" <dlopp@xxxxxxxxxxxxxxx>]

I am again surprised by the premise of being able to see two sides of a coin
at the same time- my fuzzy brain won't let me do it.? Don.
----- Original Message -----
From: "Paul Talbot" <ptww@xxxxxxxxx>
To: "Medium Format 3D Photography" <MF3D.Forum@xxxxxxxxxxxxx>
Sent: Monday, June 19, 2000 8:49 PM
Subject: [MF3D.FORUM:798] Re: I need a MF 3D Dr.


> "Dr. George A. Themelis" quoted and wrote:
>
> > >Drawing on an example I
> > >was given, let's say the closest object in a scene is a coin
> > >standing on edge, thin edge toward the camera.  Say the physical
> > >depth in the scene is not very great, and the scene is fairly
> > >close.  The MAOFD formula may yield a stereo base that is
> > >significantly larger than 1/30 the distance to the near object.
> > >It is possible that the left camera will see the "heads" side of
> > >the coin, while the right camera sees the "tails" side.  When
> > >you go to view the two images in 3D, there will be problems,
> > >even though the MAOFD has not been exceeded!
> >
> > Two comments on this:  The coin that stands on its thin
> > edge toward the camera is not a particularly good example
> > of a subject with limitted depth, especially if photographed
> > in a close up. Standing on its face would be a better example
> > but then it does not have the problem you described.
>
> To clarify the original example, the coin on its edge is
> simply the *nearest object* in the photo, not the entire
> subject matter of the photo.  We don't need to limit the
> depth THAT much for the problem to arise.
>
> > The other
> > comment is that when our eyes look at the coin on its side,
> > we do not seem to be bothered by the fact that the left eye
> > sees quite a bit of the left side and the right eye
> > sees quite a bit of the right side.
>
> Darn, why can't I think of the simple things like comparing
> the photo example to the real world!?
>
> On reading your post, I tried it.  And it DOES bother my
> eyes.  I either see a double coin, or my perception flips
> back and forth between seeing the heads and tails.  I
> cannot find a location to place the coin close to my
> eyes that I can see both sides and not be bothered by
> it.  (If held at a distance, we are not really seeing
> the sides of the coin, just a flat surface.  At a
> distance from our eyes, our "stereo base" is not wide
> enough to look *at* the sides of the coin, as a pair
> of widely spaced cameras would.)
>
> > >Extending the example to more likely real situations, it is
> > >easy to see that if the base is so large as to see different
> > >sides of a near object, fusing the two chips into a pleasing
> > >3D image could be quite difficult or impossible.
> >
> > I would think that the stereo base would have too be way
> > too large for this to be a problem in a practical situation
>
> That's a good point, but what is "way too large?"  In some
> cases the MAOFD approach recommends a base that is several
> times larger than 1/30.  I also think that when Bill first
> started studying the stereo base, he told me his spreadsheet
> comparing results sometimes had even an order of magnitude
> difference.  So there is a lot of room for "way too large"
> to occur.
>
> > and you will first ran into other problems (like insufficient
> > overlap between R and L).
>
> Yes, but doesn't that depend on the film format?  When working
> with 6x7 images to be mounted in 50x50 mounts (or shooting
> full frame 35mm and mounting to 5P), there is a lot of film
> to the sides to absorb that non-overlap area.
>
> > From DrDave's posting it seems that mounting was the problem
> > here.
>
> Way to go David!!  :-)
>
> > Our club's newsletter had a nice write up on the stereo
> > window.  I will send Bill a copy.  I think it will clarify
> > a few things about mounting and the stereo window.  Also,
> > in NSA DrDave will demonstrate mounting of stereo slides.
> > Perhaps DrDave or Paul can include MF mounting as an example?
>
> I'm incapable of MF mounting.  In fact I can't wait to see
> David's techniques (MF AND 35mm).  How many times is DrDave
> giving the workshop?  I want to see it every time and study
> his every move!!  Anyone bringing a video camera?  I want
> a copy of the tape to bring home with me!
>
> Paul Talbot
>