P3D Re: I need some help!

[Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Wed, 24 Mar 1999
>From: "Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>To: tech-3d@xxxxxxxxxxxxxxxxx, photo-3d@xxxxxxxxxxxxxxxxx
>Cc: "Bedner David" <bedner@xxxxxxxxxxxxxxxxxx>
>..........
>This was rejected from tech-3d (for unrelated technical reasons.)  
>I am posting it in both lists. ......
>
>Hallo,
>
>I'm using 2 Nikon SLR's (N90s) side by side
>to shoot stereo pairs. I use 35mm slide viewer to
>view them. It's really *grate* the view is magnificent!
>But, when I scan the slides, and try to make an Anaglyph 
>Some thing is going wrong! (I'm positive that I'm doing it right) 
>The parts in the pictures are too far from each other, and I
>Don't see any stereo effect.
>
>My questions are:
>
>    1.. Is any body using 2 large SLR's (like N90s) side by side? 
>    2.. Can the "stereo base" be grate for slide viewer; 
>        but wrong for an anaglyph?
>    3.. Should I replace one of my N90s for 2 little cameras, 
>        to reduce the "stereo base"?
>    4.. Info: I use 28-70mm lens(es), and the stereo base is 170mm. 
>
>I'll be grateful for any help!
>


****  You haven't described *how* you are doing your anaglyphs.

For starters, using side by side Nikon's creates a bit of trimming work with
the images. There is side image content not present in the other image, for
both sides. As slides in a viewer it's easy to ignore this excess area, but
when you make an anaglyph without trimming first it doesn't work right. The
slides would be easier to view too, if you mask the excess image content.

In effect you have the entire image projecting in front of your stereo
window. That would make your anaglyph hard to view.

Once the images are scanned, you need to trim enough of the excess image
content to set the window in *front of most or all of the rest of the
image*. Once you've done that carefully you're anaglyph will turn out better.

Freeviewing while you edit is the easiest way to determine where to trim. If
you don't have that skill, here are a few other things you can do. Look for
the nearest objects in the scene. Trim the side edges until the closest
object in the scene is exactly equal distances from the right and left edge
*in both pictures*.

Note, this does NOT mean they have to be in the center of the image. It
means that between L and R images, they are located the same... Using *x*
for pixels and *()* for the closest image element, here's an ascii drawing
to help understand the principle. In this case I'm placing the L image on
the left and the R image on the right... parallel viewing.

|xxxxx () xxxxxxxxxx|       |xxxxx () xxxxxxxxxx|

Or 

|xxxxxxxx () xxx|       |xxxxxxxx () xxx|

Once this is true in your images, the closest point will be located AT the
stereo window. This is a good starting point for you to evaluate your final
results. Make an anaglyph to check it out. 

If you want the closest detail in the image to be just behind the window,
you can easily make another small adjustment...

|xxxxx() xxxxxxxxxx|       |xxxxx ()xxxxxxxxxx|

Or

|xxxxxxxx() xxx|       |xxxxxxxx ()xxx|

Now you are ready to make an anglyph that works right.


>    3.. Should I replace one of my N90s for 2 little cameras, 
>        to reduce the "stereo base"?
>    4.. Info: I use 28-70mm lens(es), and the stereo base is 170mm. 

This depends on what you want to shoot. If you want subjects within 20 feet
or so, the smaller cameras allow a smaller stereo base, which will work better.

If you are shooting landscapes at greater distances, or large buildings or
objects and your distance from the scene is quite a ways, your existing
arrangement is fine, or you may need to increase the distance between them.
Remember that when using a wide stereo base, you need to avoid close objects
in the scene, or cut them out later. (like the lawn of a large house.)

For closer subjects you might try putting the cameras together bottom to
bottom. The images will be in a vertical format, but for closer subjects
that's a better stereo base.

Good luck,
Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/
http://3dzine.simplenet.com/


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