[MF3D.FORUM:1664] Re: Using front shift to simulate camera movements?

[Tom Hubin <thubin@xxxxxxxxx>]

Hello Don,

Not true. It depends entirely on how you do it. If you connect all
points on the subject to all points on the lens and the mirror
intersects all of those rays then you loose nothing.

For stereo there is a practical limit on this single mirror approach.
The system is creating the illusion that the lenses are side by side
with the camera bodies overlapping. They cannot appear closer than
touching each other without clipping something. For example, if the
lenses are 50mm diameter then 50mm is the smallest interocular that you
can create without clipping.

To avoid clipping at 45 degrees you need a mirror that is the square
root of 2 larger in the folded dimension. So a minimum of 50mm by 71mm
ellipse would be needed in the above example. 

Tom Hubin
thubin@xxxxxxxxx

**************************************

Don Lopp wrote:
> 
> Plus the angle covered would be relatively narrow DON

> ----- Original Message -----
> From: "Bill Glickman" <bglick@xxxxxxxx>
> To: "Medium Format 3D Photography" <MF3D.Forum@xxxxxxxxxxxxx>
> Sent: Wednesday, April 11, 2001 12:31 AM
> Subject: [MF3D.FORUM:1657] Re: Using front shift to simulate camera
> movements?
> 
> > Tom
> >
> >         I'm not understanding this....  If you look forward you see an
> > image, if you turn 90 deg and use one mirror at 45 deg, you will see the
> > same image.  So why wouldn't the film see the same thing looking in the
> > mirror?  Are you sure you would have to view the slide with the emulsion
> > side away from our eyes to get the same effect as if the cameras shot
> > straight at the scene?  Hmmmm..if so, that does not sound good, but then
> > again we look straight through the slides anyway?
> >
> > Bill g
> >
> > > Clever idea but the images will be mirrored. So you will need to print
> > > with the emulsion side up or view slides with the emulsion side away
> > > from the eye or project with the emulsion side away from the screen.
> > > This will reduce the quality of the image.
> > >
> > > A pair (or any even number) of mirrors for each camera is more
> > > complicated but would avoid the mirror image problem. For that matter,
> > > two mirrors on one camera and no mirrors on the other camera would also
> > > work. But then the distance from camera lens to subject is not the same
> > > for both cameras.
> > >
> > > Tom Hubin
> > > thubin@xxxxxxxxx
> > >
> > > **********************************
> > >
> > > Matthew V. Ellsworth wrote:
> > > >
> > > > Bill
> > > > I'm not sure if I'm understanding what you want to do, but maybe this
> > idea will
> > > > help:
> > > > Two cameras can be mounted facing each other on an adjustable rail --
> > with a
> > > > small front-surface mirror mounted at a 45 degree angle in front of
> each
> > lens.
> > > > This allows you to get both cameras quite close (limited by the size
> of
> > the
> > > > mirrors), and allows easy access to the focusing and film advance
> > mechanisms.
> > > > Matt
> > > >
> > > > Bill Glickman wrote:
> > > >
> > > > >       I am trying to develop a MF camera system that allows one to
> set
> > > > > interocular bases at any seperation without physical
> > limitations.....As we
> > > > > all know, this is physcially impossible sometimes with two non-
> shift
> > > > > cameras.  My idea was to use two cameras side by side, but each one
> > would
> > > > > have the capability to shift the lens horizontally.   This has a
> very
> > > > > dramatic effect vs. spacing the cameras.  For example, I can
> simulate
> > 24"
> > > > > interocular distance with only 3mm of front shift on one camera.  I
> > have
> > > > > tested this, it works.  So a small amount of lens shift would
> simulate
> > > > > interocular spacing fro 0 to 500 + ft.
> > > > >
> > > > >       I have found that myself and my audience all prefer very small
> > OFD's,
> > > > > say 1.3mm, hence the need for bases much tigher than any two cameras
> > can
> > > > > every physically acheive.   A fixed stereo camera (sputnicks) don't
> > appeal
> > > > > to me because I want the flexibility of adjusting the interocular
> > distance
> > > > > when required.
> > > > >
> > > > >         Although this sounds good in theory, I am curious if this
> will
> > > > > produce the same stereo effect as utilizing two cameras at the
> proper
> > > > > interocular distance.  I don't plan to use it for excessive bases,
> > only for
> > > > > 24" and less.  Has anyone every tried this before?  Any input?
> > > > >
> > > > > Bill G
> > > >
> > > > --
> > > > ______ Matthew V. Ellsworth ______________________________
> > > >       oakridge@xxxxxxxxxxxxx      http://www.oak-ridge.com
> > >
> >
> >