[MF3D.FORUM:556] Re: Exact fl match for paired lenses.

["David Lee" <koganlee@xxxxxxxxxxxxx>]

Bill,

There have been so many suggestions made at this point that you are probably
more confused than ever. I will try to make this as simple and uncomplicated
as possible. First of all, I believe that orthostereo is highly over-rated,
especially for landscape subjects. I hardly ever use camera separations
closer than 5" (my medium format cameras will get down to 4"). My large
format cameras will only go down to 5.5". I had originally thought this was
going to be a major problem, but it has not been a problem at all. I even
spent a lot of time designing mirrored systems such as the kind mentioned,
so that the cameras could be turned to the side. One version would have had
a mirror inside each camera and the other version would have had regular
cameras with mirrors between them. At this point I have no more desire to
make them since 5.5" is turning out to be perfectly adequate for me. Now
this doesn't mean that it will be adequate for you (or anyone else), since
you may be interested in shooting subjects which are closer to the camera
than I am interested in. However, lets first examine what this means in
practice before we jump to an expensive and complicated solution to a
situation that may not be a problem. Let's start by taking your situation.
80mm lenses (normal) with a near point of 8' and a far point of 20'.
According to the formula I use (and I am pretty certain it coincides with
that of John B.), that would result in a separation of 5.3". This will give
excellent stereo and there will be no eyestrain for the average viewer. This
will also result in more extraneous image at the edges and you may have to
make your own mount (it's really not hard) to make it narrower. But you will
not be losing all that much. In fact, I would be willing to bet that the
regular mount for 6x6 would work perfectly.

Yes, images from 7' to infinity will probably not be a viable option with a
5" separation, but 10' to infinity would work just fine (although it would
be pushing it slightly). What makes most of the situations I shoot work so
well is that I often am able to eliminate infinity and this makes a
remarkable difference in the calculated separation. As I mentioned in a
previous message, if the far point is no more than twice as far as the near
point (say, 7' to 14', for instance), then the formula results in twice as
much separation as it would if it went to infinity. In the case of  7' to
14' the separation would be 5.6", whereas if it were 7' to infinity it would
be 2.8".  It's not always possible to do this, but before you try some of
the solutions mentioned I suggest you get some 6x6 mounts and shoot a few
more rolls. No system works perfectly in every situation, but (I will repeat
again) I believe you may have the best system for landscape stereography
that money can buy -- JUST LIKE IT IS.

If you must make modifications in order to get a narrower base, the most
cost and time effective one would be to build a device (or buy one from
Jasper Engineering) that will allow you to turn them on their sides (that's
what I was going to do when I was thinking about purchasing Mamiya 6's).

David Lee

> So it seemed that was the only position to put the right chrome... and
> everytime I did this, the edges of the scene would have double vision,
about
> 25% at each edge, while the center 50% was fabulous, or WOW.  So I felt
this
> was the only place the right chrome could go?  No matter where else I
moved
> it to, it would not create a fused image in the middle?  So where do you
> think I went wrong?
>
Probably you need narrower mounts. If I had them in front of me I could tell
you exactly what to do. Send some to me if you'd like and I'll give you a
more certain answer. I could also tell you if there was too much lens
separation or not.

David Lee
3664 Hardin Way
Soquel, CA 95073