Re: [photo-3d] Checking & adjusting alignment by projection

[Project3D@xxxxxxx]

In a message dated 31/03/01 19:25:01 GMT Daylight Time, George Themelis wrote:

<< Last night I was preparing the "Easter in Greece" stereo 
 slide program, for my Greek class on Monday.  I selected
 50 slides, mounted all of them in RBT mounts, put them in 
 an RBT 50-slide tray and checked the tray out. I noticed
 a couple of slides had a vertical alignment error. 
 
<<SNIPPED>>
 
 Question: What contributes to this misalignment and
 why it cannot be seen in the viewer?  The problem IMO
 is the fact that some times the two halves of the
 RBT mount do not overlap perfectly. 0.1mm is a small
 vertical step and it can be missed, but it becomes
 clear in projection.>>

First, it _can_ be seen in the viewer, but learning to see it is rather like 
learning to free view! If you look at a slide with a small vertical error in 
a hand viewer and study the top and bottom edges critically, you may become 
aware of what I can only describe as a slight "greying" of the edge. The 
worse the error the greyer the edge will be! 

I suspect the misalignment problem is more likely to be caused by the film 
wandering in the camera. I'm assuming all the slides are from one camera, but 
if not, then the answer is even easier! Some cameras have a small, constant 
error. So, if your show was a mixture from different cameras... 

<<SNIPPED>>

<< BTW, here is my new personal stereo projection setup:  
 
 I am sitting at the kitchen table, 8 feet from the 50 in. 
 screen.  The RBT projector is right behind me on the 
 kitchen counter.  I hold the wired-remote to change slides 
 and adjust the focus, R/L independently or both together.  
 The projector is fitted with 85mm/2.8 lenses.  I got these 
 lenses from ebay, brand new for $30 a piece!  They are made 
 by Will-Wetzlar in Germany!  Good quality.  Leica mount.  
 3 1/3" focal length. Shorter than the desirable 4" TDC 
 lenses.  (I am now investigating if I could use these
 lenses in a TDC projector too - stay tuned!)>>

Whilst those lenses will be fine for your slide previewing, I've found them 
to be a bit softer than the modern lenses...

And one question. Why do you put your slides in the tray before checking them 
in the projector? I would drop them in one-by-one and make any adjustments 
immediately without having to take notes of which slide and what to change... 
Drop them in the tray once they pass muster!
 
 Bob Aldridge
Stereoscopic Society Projectionist

 

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