P3D Re: Circular Fisheye photos

[Larry Berlin <lberlin@xxxxxxxxx>]

> Date:   Mon, 20 Dec 1999 
> From: Greg Erker <erker@xxxxxxxxxxxxxx>
> To: photo-3d@xxxxxxxxxxxxxxxxx
> ...... (I commented).........
> >It seems the fisheye lens brings infinity up to about 50 feet distant.
> >Perhaps the stereo results would be more interesting with more content
> >near the camera?
> 
>   I'm not sure how you can tell that infinity
> is at 50'. I usually mount to the window so
> my infinity spacings will vary depending on
> the nearest objects.

****  It has nothing to do with your mounting. Most noticeable depth
parallax in your image disappears somewhere just in front of the central
bridge support. The estimate of 50 feet could be off by quite a bit,
since it was a guess. The point was, the near foreground had lots of
visible depth which tapered off rapidly until by the point of the bridge
and beyond there was little depth at all that could be seen or detected
by careful triangulation. The bridge -appears- just as far away as the
horizon.

In stereo images with infinity, it's usually that point at which things
seem to flatten out and nothing is more distant. Distant mountain ranges
in a Realist photo look as flat as a wall, and equally distant as the
horizon. Those seeking an *Ortho* experience sometimes point out that to
your real eyes, you can't see any depth on that distant mountain anyway.
That's realism.

The idea of infinity is, that's the farthest point you can visualize in
a sense of depth. In the fisheye image, lots of content that is
obviously nearer than the horizon, looks no closer than the actual
horizon. I'm sure it's due to the fish eye lens. Therefore I said it
brings the infinity point near your picture taking location.


> .......
>   I do need to take some shots that show more
> depth, rather than just the grass and tripod
> legs below the camera.

****  That's why I commented on the infinity factor. If you do NOT have
a visible infinity like the horizon in your image, and all that is
contained in it is less than (approx) 50 feet away, you will have a more
interesting image in terms of depth presentation. Most of it will have
visible depth relationships. 

It's not a problem, it's just the geometry of working with a fisheye for
stereo.


.......
> > The Moss image is quite unique. Very nice.

>   That one is very sharp seen in my MF viewer.
> But the stereo window violation bothers me a
> bit.

*****  It loses the violation factor if completely surrounded by black
areas. Then it's like a cylinder of image free floating in space. This
is another case where freeviewing offers an advantage due to the change
of effective viewing focal length, as compared to looking into an MF
viewer. 

Then too, you could edit the image to push the entire view behind the
window. I know, that's hard to do with an MF transparency... but
selective masking might work.

Larry Berlin

3D Webscapes
lberlin@xxxxxxxxx
http://3dzine.simplenet.com
*-) ---> :-) ---> 8-) ---> 8-O