[tech-3d] RE: Different F.L.s

["Chuck" <cfholzner@xxxxxxxx>]

> > --- In tech-3d@xxxx, siggyblue@xxxx wrote:
> Thanks Chuck.  I all ready know about increasing the focal length
> to match the print enlargement.  the problem is the viewer F.L. is
> around 230mm. If I were to preportionally increase my views they
> would be much larger than is possible to view.

True, You would need to either crop your photos, use prismatic lenses to
increase the distance between the prints, or use a shorter focal length on
the viewer lenses.

> What do you mean by ortho?

Orthoscopic.  Objects in the viewer look to be the same size and distance
from you as they did when you were at the sight taking the picture.  When
you said that you heard that the viewer lens FL should match the Camera's,
You were implying "Orthoscopic".  If you are not looking for "orthoscopic"
then the FL's become variables to be used in various formulas to allow
deviation from orthoscopic and yet allow the picture to be viewed in
comfort.

> When you say a longer focal length "increases the depth".  Do
> you mean the viewers perception of depth?  Or are you referring
> to the actual distance from lens to print?

Viewers perception.  A longer focal length of the viewing lenses leads to an
exaggeration of the depth, whereas too short a focal length produces the
opposite effect.


You should get a copy of "Stereo Photograph" by Fritz G. Waack DGPh AFIAP.
Reel 3D Enterprises sells it.

Chuck


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