[MF3D.FORUM:559] Re: Exact fl match for paired lenses.

["Bill Glickman" <bglick@xxxxxxxx>]

David

I love the tone of your message...You have some great points...

> 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").

That is very encourging to me.  My min. camera seperation is... if both
horizontal, 6.5" both vertical 5.5".   I just measured this very
accurately... so in case my earlier guestimates were slightly off... these
numbers are official.  Rembeber you were estimating for M6, which was 6x6,
so the cameras would come closer by at least 2 cm or more...about an inch...
Those would have been a bit better.  But I already owned one M7.


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.

I like the sounds of this, no more expenditures $$$  !!!

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".

Yes, this is the same as John B fourmula...keep going...


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.

What exactly do you mean by extraneous image at the edges?  Does this mean
can not fuse subjects together, or subjects in one chrome but not the other?

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.

       I used the 6x6 mounts from RMM, but they all created huge double
vision on the edges.  The centers were perfect stereo!  But 25% out to the
edges were could not be fused.

> 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.

This is an excellent point and makes this whole thing seem more feasable.  I
never played with the formula enough to have that type of knowledge.  After
experimenting with the formula I noticed also, the near is critical, the
further away the near is, the safer the formula.... I had some shots like
that, I will go try to remount them and report back to you..

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.

        I am re energized!
>
> 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).

       As mentioned above, does not help much.  Either way these lenses are
too far apart to even come close to 65mm, regardless of how they are
mounted.

       The only puzzling part to all this..... All 8 stereo pairs I shot did
not have infinity in the scene.... but its possible the near subject was
closer than 8 feet, I had a hard time getting rid of the grass!   I will re
experiment with this...

Thank you David

Bill G




>
> 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
>