Re: [photo-3d] viewer optics

["Alan Lewis" <3-d@xxxxxxxx>]

Paul wrote:
> Re: Ferwerda's comment that 'the eccentric viewing may give
> an unfavorable effect when the lenses are of a very simple
> quality,' Peter Abrahams (2001-03-08) suggests:
>
>   | the effect would very likely extend to other types of
>   | lenses than 'very simple', especially when they are f2.

Now let's look at the same book in section 3.4 for even another opinion.

I think this topic gets a bit off issue sometimes.  Section 3.4 in the book
tries to illuminate us as to why interocular adj. is in some viewers.  I
tried to do that too but it was mis-interpreted I think.

I have already stated this, but I'll try again:
Adjustable viewer interocular is OK to have but not necessary if the viewer
is designed correctly and the mounting standards are followed.  I stated
that my viewers are designed for use with mounting standards.
Therefore there is very little at issue here.  If one does not want to
follow mounting standards then they may not be pleased with my viewers.  It
is up to the individual.  But I don't think the blame should be placed on
the use of large diameter, fixed spacing lenses.  The only issue is what
mounting standard do you ahere to.

One reason I have chosen this path of following mounting standards is to try
to direct the medium format stereo enthusiast into producing a consistantly
mounted image that can be instantly and comfortably fused by almost anyone
with any eye spacing.  I try to encourage good consistant mounting
practices.  Again, if this goal does not fit within one's belief pattern
then they may not like my viewers.

Mounting to the window does not automatically disagree with my viewer design
standard.  It is only the maximum infinity separation that would do that.
If you mount to the window and your infinity separation does not exceed 66mm
(it can vary, just not exceed) then you should enjoy your slide in my
viewer.  I mount to either the near point or the far point with my slides
depending upon what is in the image.  If infinity is in the image I mount to
infinity.  If it is not then I mount to anything I want, even through the
window, but I check the infinity spacing compared to the maximum standard.

If I were to design a viewer using adj. lens spacing I would still use large
diameter lenses.   I judge viewer performance on both image quality and
comfort of use.  Large diameter lenses offer a much more comfortable viewing
condition for people who wear eyeglasses than smaller dia. lenses do,  a
better field of view.

Please read section 3.4 (which links to section 5.3) in Ferwerda's book to
understand better where I am coming from.  I seem to be doing a bad job
getting my view across in an understandable fashion.

Let's try and re-direct the topic here:
All of us accept the concept of "vertical alignment error" and "rotational
error".  Why don't we use the term "horizontal error"?  Both vertical and
rotational adjustments in the mount have some form of maximum amount before
they become objectionable and therefore are re-classified from "adjustment"
to "error".  Why don't we agree that at some point of the horizontal
adjustment it also becomes an "error" rather than an adjustment?  Even a
viewer with interocular adjustment has a maximum distance of separation, so
there must some standard at work here.

Alan Lewis
3-d@xxxxxxxx
Serious viewers for serious Viewers
http://members.home.net/3-d




 

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