P3D Re: RBT X3A lens spacing

["David W. Kesner" <drdave@xxxxxxxxxx>]

In p3d digest 3221 Greg Wageman replies to my post:

> Have you measured your own interocular?

No, but my eye doctor has *{;-) He says it is 64.5mm so the 65mm 
inter-lens spacing of the X3A is the closest to ortho that I can get for 
myself.

> Mine is closer to 70mm

You are then lucky enough to go either way (65 or 75mm) and not 
notice too much of difference. However, 10mm does make a 
perceptible difference to me.

>(For example, I know that people in
> general are considerably taller, on average, than they were during
> colonial times. Are our eyes wider, too?)

Does this mean that we will eventually look like all those alien 
representations with huge, wide spaced eyes?

> "Universally accepted"?  Define please.

I didn't mean to offend any format or equipment by this comment. 
What I meant was that 28x23mm aperatures in 41x101 single 
mounts was the largest that I could go and still be reasonably 
assured that any where I went there would be equipment that could 
be used. That means stereo clubs, SSA folios, PSA stereo 
exhibitions, and most any stereo slide enthusiast's home.

Yes, other formats can be entered in folios and competitions, and 
some clubs have varied viewers and projectors, as well as 
enthusiasts. But I would dare say they are in the minority. I don't 
want to start this tread again, but I would liken it to Mac versus 
Windows. Both are good and everywhere, but if I had a great 
program I wanted to share with as many people as possible I would 
carry it around in a Windows based format. Please don't comment 
on this analogy!

I would also say that the larger the format the better: 5p is better 
than 4p; 7p is better than 5p; full frame is better than 7p; and 
medium format blows them all away. But how many medium format 
projectors and viewers are there? Is there even one medium format 
stereo slide competition?

This is NOT to say that a 4p slide can't be better than a 7p. There 
are other factors such as composition, but if ALL else is equal - the 
larger the image area the better.

>  There are many stereo
> projectors which will not project a 7-perf slide in its entirety
> without modification, and I seem to recall mention of some that won't
> do it at all.

I just recently learned that not all TDC projectors can show 7p. Mine 
does, so I assumed that all could.

> By your definition of "waste", practically every stereo mount in
> existence "wastes" film, because they all mask part of the image to
> set the window.

What I meant by waste was that if you know you are going to be 
mounting all your shots in 7p then there is no need to use a full 
frame when you can get two more pairs in every roll of film. When 
you shoot hundreds of rolls every year like I do, those really add up.

> I find it very helpful to have "extra" image area to work with,
> especially when some element that I didn't catch in the viewfinder
> creeps in at the edges.  The wider the original image area was, the
> less you have to sacrifice when you are forced to crop due to window
> violation or whatever.  Worst case, I have mounted a full-frame image
> in a 5-perf mount and "saved" an otherwise-ruined (compositionally
> poor grab shot) image.  I don't call that wasting film; that's saving
> film!

I agree with you on being able to mask down and that the larger the 
area you begin with the more you can mask down. That is one of 
the reasons I use the Spicer mounts. I start with a 31.5x24mm chip 
from the RBT X3A. I can use a 28x23; 28x20; 26x23; 21.5x23; 
21.5x20; 19x23; 16x21 to my advantage in window placement, 
composition, or masking. But hopefully those shots that need to be 
"saved" are few and far between and a decision to buy a particular 
model of camera shouldn't be based on just those few shots.

> If you've ever seen panoramic
> stereo (it was shown at NSA in Bellevue) you'd never want to go back
> to 5-perf!

I did get to see the panoramics and they were great. However, 
when you get to that extreme of proportions (length to width) you 
have really narrowed your field of subject matter. You just can't do a 
portrait in this panoramic format unless you want a whole lot of 
something else in the shot.

Lastly I would like to say that 1950's Realist format cameras taking 
5p size film chips produce every bit as good a final product as a full 
frame RBT camera. Just take a look at the winning entries in PSA 
exhibitions or join an SSA folio and see all the truly wonderful work 
done by these cameras and stereo photographers.

I was just giving my reasons for choosing the camera I did in hopes 
it would help others in the search for theirs.

That's all for now,

David W. Kesner
Boise, Idaho, USA
drdave@xxxxxxxxxx


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