Hi Richard:

Pin registered mounts, when projected in the professional line of Kodak 
Ektagraphic projectors, would gate the same way, every time - for all 
practical purposes would gate registered. Much of this had to do with 
both the tolerance of the slide projector gate and the Wess mount, which 
was very thick, very heavy and consistently manufactured by Wess. The 
mount was two pieces and hinged on one end. It would snap together and 
lock closed. Inside, it had three pins which matched the sprockets in 
the 35mm film and held the film registered in the mount. You could put 
an alignment slide in a projector, align it to a point on screen and 
cycle it over and over. Every time it would gate and project in the 
exact same spot on the screen.

The other optical company out of Rochester was Navitar. The owner was 
Julian Goldstein. They were famous for making the highest precision-made 
slide projector lenses in the industry. Later I believe they became 
known as D.O. Industries. Among other lenses, they made a great PC 
(perspective control) lens and a monster Golden Navitar 6X9" zoom lens 
that was so big, it needed a custom bracket that attached to the front 
of an Ektagraphic projector with an additional foot support forward of 
the projector on the bracket. Without the support, the weight of the 
lens would tilt the projector down and forward. I believe it had an 
f-stop of 4.6, which for long focal length of the lens, was quite fast. 
The image projected though a Navitar lens was very clean and crisp.

Where you say A, B and flash, I understand what you are saying. This was 
a common design for multi-image programs where a background was held for 
a period of time and images were inserted in boxes or other types of 
image hold-back designs on the background. Actually any projectors in 
the bank could hold the background slide, with other projectors being 
insert images for the background. You would want to cycle or change the 
projector that held the background, from time to time, so that you don't 
end up with one projector that just held one background slide image in 
the tray while the two other projectors had full trays of insert images. 
Cycling the background slide from projector to projector gave you more 
total slides to project (if needed). Also in most shows, the design of 
the backgrounds would change from time to time throughout the show, 
allowing you to switch which projector held that background. Simple 
shows would dissolve between two projectors with a third holding the 
background. In more complex programs there could be six, nine or twelve 
projectors in a nest/bank and backgrounds would change constantly with 
the remaining slide projectors filling the insert boxes in the background.

For the 16mm film, since it was inserted into a box in the background as 
a smaller image on the 35mm background, 16mm inserts could look quite 
decent, though it was an added expense of shooting 16mm film and the 
added hassle of something going wrong in the staging of the program. As 
I referred in a past email to Mike Biel, a 35mm Nikon with a fat back 
and a motor drive, shooting slide film could provide plenty of realistic 
movement when cycled through a group of projectors. Usually when we used 
a 16mm motion picture film insert, it was to refer back to historical 
content in the middle of the slide presentation and in that context, it 
was very acceptable when playing the part of telling a story.

Kind Regards,

John Schroth
Media Transfer Service, LLC

On 8/6/2012 2:11 PM, Richard L. Hess wrote:
> Hi, John,
> Thank you so much for filling in so much more information--at a higher 
> level--than I was ever involved in.
> I agree, a good slide-tape-film show can be truly inspiring and 
> immersive. I had forgotten the joys (??) of pin-registration.
> How did pin-registered mounts register in Carousel projectors?
> I remember Chief stands and there was another optical company (other 
> than Buhl) who was servicing this industry. I think Buhl was out of 
> Pittsburgh and the other company was out of Rochester.
> I _think_ The New York Experience was using a 1/2-inch 4-track tape 
> machine--an audio format that was considered more "professional" than 
> the 1/4-inch 4-track that you mentioned. And yes, their "machine 
> sitter" in the booth was there because of the well-known cantankerous 
> nature of these shows. They were certainly not a kiosk computer 
> playing back a PowerPoint.
> The point I think I was originally trying to make was that properly 
> archiving one of these shows is very difficult to retain full impact. 
> I doubt that many (if any) of these will ever be seen again in their 
> full glory. If we wanted to classify these as "formats", we would 
> probably need to classify each configuration with each manufacturer's 
> control protocol as a separate "format". You did mention the two-wide 
> with centre overlay as a common format. I do recall seeing a number of 
> these at National Park venues. I was thinking about the more elaborate 
> ones that added another panel and another splice (at least) for five 
> stacks of projectors.
> While this is beyond my personal experience, I think I recall three 
> projectors being common in a stack: A, B, and "Flash" where A and B 
> dissolved into each other and the "Flash" projector would show an 
> overlay independent of A and B.
> I _think_ I've also seen film shown in a window created by a slide 
> (i.e. there was a totally black area in the slide and that's where the 
> film hit the screen). You couldn't really use 16 mm film at the same 
> size as a 35 mm slide as the film's much lower resolution would be 
> immediately obvious.
> Ahh, the complexities we used to go to...
> Cheers,
> Richard
> On 2012-08-06 11:59 AM, John Schroth wrote:
>> I majored in Multi-image slide presentation at RIT over 25 years ago. 
>> They had a core-curriculum in Multi-Image slide production, the only 
>> one like it in country at the time. I have produced many of these 
>> programs while at the college and at a production company where I 
>> worked for quite a few years after graduating.