P3D Re: Realist system flawed?

[john bercovitz <bercov@xxxxxxxxxxx>]

> Boris says that the Realist system is significantly flawed because it
> is non-ortho stereoscopic.  What Boris means is that the focal length
> of the lenses in the Realist camera (which is 35 mm) does not match the
> focal length of the Realist viewers (which is 44 mm)
> 
> How important is that mismatch?  Is it noticeable?  What effect does it
> have?  

It becomes less noticeable with time but when you first view stereo 
slides from too far back, the effect is simply shocking, at least it 
was for me.  Still is, to a degree, but I've not been able to sit the 
right distance from the screen often enough that I can bear it now.

> Ordinary, 2D photography, is also non orthoscopic.  We view our 4" prints
> from a distance longer than the ortho position.  To make things worse, 35
> mm lenses are consider the standard FL in many cameras.  When we go to the

I think when 35 mm photography started (correct me here, BobH) that 
a lot of people took slides and so 50 mm was great because then people 
sitting at 2X screen image height, which is roughly where they wanted to 
sit anyway, were in the ortho seat.  (Yes, Virginnia, there is an ortho 
seat for mono photography too, as Dr. T said.)  When people switched to 
small prints, they should also have switched to 100 mm lenses.  I'll 
never forget seeing the first shots from my dad's Nikon F when he got a 
longer (~100 mm) lens for it.  My reaction was, "Aha!  So _that's_ what 
was wrong!"  This was before I knew anything about perspective.  I went 
right out and bought a 100 mm FD for my Cannon and have been using it 
ever since for prints.  (Still use 50 for slides, though.)  People like 
35 mm lenses for all the "perspective" they get and manufacturers like 
them because they can sell small P&S glass for big money.

> The judges that selected Boris' pictures for awards I bet were also sitting
> well behind the ortho seats.

They were sitting at 9' and the projector with 4" lenses was sitting 
at 18'.  So they were sitting at the 50 mm spot.  A bit longer even 
than the Realist red button.  However, there was one person arguing 
that they should sit even further back for the best effect!  8-)  The 
projector was at 18' so that we could have the 7P slides on the same 
screen as the 5P, the 6' screen being square.

> Boris is also doing table top
> photography which requires much smaller lens' separation. 

Not necessarily.  I took some the other day (sent some copies to Jamie).
67 mm separation, 55 mm lens, 250 mm from lens to subject.  Works fine.  
No problem with "viewability" but I did limit scene depth*. And so of 
course I agree with your statements further on regarding the reason 7' 
is the nominal window distance and near point for the Realist.  
*Had to - if for no other reason than because I can only go down to f/32 
and I already lose too much res at that f/no.  I like my slides to be 
"viewer sharp", not just "screen sharp".  

> Conclusion:  Yes, the Realist type viewers are longer in FL than the
> Realist camera lenses.  No, for most people and most subjects this
> mismatch is not disturbing, to the point of calling it a "serious flaw". 
> For most people (but certainly not all), the Realist system is a better
> way (read: cheaper, more convenient) to get started in good quality stereo.

I have to agree with this.  I might say "most people and many subjects" 
but that's nitpicking.  I think most people can tell that a car or a 
person is stretched if the photo is taken at any reasonably close 
distance and lots of pictures which include cars and people are taken.

John B


------------------------------

End of PHOTO-3D Digest 2583
***************************