[MF3D.FORUM:1656] Re: Using front shift to simulate camera movements?

[Tom Hubin <thubin@xxxxxxxxx>]

Bill Glickman wrote:
> 
> Matt,
> 
> > 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

>         Thanks for the suggestion Matt.  Have you ever tried this before?
> How is the results?  I would assume the mirors would introduce some
> sharpness loss?   Also, how do you determine your interocular distances?  Is
> it the measurement between the center of the mirors?
> 

Hello Bill,

The mirrors will only hurt the image quality if the mirrors are poor
quality. You will need good quality first surface mirrors. You will need
to keep them clean and damage free. Gentle and loving care just like for
your camera lenses.

Inexpensive aluminum mirrors reflect about 85% of the light. Some
mirrors with better coatings can reflect more light, more like 95% or
98%. Get info on light losses and make sure that is ok before you invest
time or money in the wrong mirrors. You will need high reflectance
mirrors if you shoot in low lighting and cannot afford to give any light
up. 

The interocular distance is, for practical purposes, the mirror
sepertion. The way it actually works is to draw a line from the subject
to the mirror and then add to it the distance from mirror to lens. This
locates the image of the lens as seen from the subject. Since the
mirrors are very close to the camera, compared to the distance to the
subject, the interocular distance is just a touch more then the distance
between mirror centers.

If you do this with more than one mirror per camera then the seperation
of the mirrors nearest the subject will, as a practical matter,
determine the interocular.

If you do this for close subjects then the interocular needs to be
determined more rigorously.

Tom Hubin
thubin@xxxxxxxxx