Brackett Dissolver

[P3D KENNETH LUKER <KLUKER@xxxxxxxxxxxxxxxxxxxxxxx>]

I've finally seen something I'd only read about on this list, and I
saw it in Stereo!  Two of them in the same room!  I'm talking about
the fabled Brackett Dissolver.  Last night the Utah Stereo Society
met for their monthly meeting, this time in Provo.  Dr. Robinson, a
surgeon who had spent a couple of years in Saudi Arabia on medical
assignment, showed us the stereo slides of his stay, including shots
of the barren and craggy wastes of the wadis and inland wildernesses,
the hilltop towns with their exotic architecture, and the austere and
isolated but modern hospital compounds where he worked.

The pictures were interesting, but I was somewhat more interested in
the projector he used.  He had a brand-new-looking, black-enameled
metal box, with four Kodak Ektagraphic lenses almost flush with the
front panel, extending toward the screen like a battery of Guns of
Navarone.  It was a formidible sight, and performed as well as I
might have expected. 

Because he had had trouble setting up the projector during a dry run
earlier in the day, Dr. Robinsons called his friend and asked him to
bring HIS Brackett Dissolver as a backup. In the event, we didn't
have to switch projectors because the first one worked wonderfully,
(after we'd switched screens--the first one inadvertently had been a
flat-white matte screen, not a silver one). I've reviewed the
material on the Brackett Dissolver in the archives and I don't find
a description of the device itself, so I'll give a brief description
here for those who may never have heard of it. The projector was
manufactured as recently as last year, but I haven't heard whether
the last batch was fully subscribed for.  My guess is that it was.
Bob Brackett of East Sandwich Massachusetts is the designer and
manufacturer.  The last cost I saw in the archives was something like
$1,750 plus lenses.

The projector features four side-by-side identical optical paths,
including halogen lamps with reflectors built in, heat absorbing
glass, dual condenser lenses, polarizers and lenses.  The framing
and focus controls are ganged so that the window can be set
independently for each pair.  Rough focus is made by sliding the
lenses forward or backward with the fingers.  Fine focus is available
for one lens of each pair and for both lenses of a pair together. 
Vertical and horizontal controls are available for each pair also. 
It would appear that one should set the projector up for a perfectly
framed and mounted slide, and then leave the adjustments untouched
during the presentation.

The unique function of the dissolver is embodied in the way the
successive views are presented to the audience.  The slides are
placed manually into the optical path by inserting them alternately
into the left and right light streams through broad openings in the
top of the projector. There is room to put the fingers down into the
gate receptacle while holding the slide, and to place the bottom edge
(top of the inverted picture) into a spring-loaded guide.  Then the
slide is pressed downward, depressing the guide, and the upper edge
of the slide (bottom of the picture) is pressed lightly backward to
fit under the upper guide, thus holding the slide exactly and firmly
in the focal plane.  During this operation, the lamps for the two
optical paths to be used by the inserted slide are dark.  The
operator then moves a lever, centered at the top front of the
projector, giving it a half turn from pointing left to pointing
right, or vice versa alternately.  As the lever turns, the lamps turn
on at a rate determined by how quickly the lever is turned. 
Simultaneously, the lamps in the other pair of optical paths fades
off.  The picture on the screen thus blends evenly from full display
of one slide into full display of the other. If the windows are
aligned and the slides are properly mounted, the effect is
spectacular.

With the new slide now displayed, the operator can press the old,
darkened slide, lightly downward and release it from the upper
guide, then lift it out and replace it with the next slide in
sequence, and so on.  The top rear of the projector has attached to
it a tiltable tray on which full and empty slide trays can be set to
give easy access to and re-storage of the slides in the show.

Having heard about but not seen these projectors before, I was
impressed.  I'd like to know how many of these projectors were made. 
Date: Fri, 24 Jan 1997 14:17:53 -0600
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Of course, I'd love to own one sometime.   Anyone wanna trade for my
116? :) :).

Ken Luker
_______________________________________________________________

Kenneth Luker, Assistant Director
Systems and Technical Services
Marriott Library
University of Utah
Salt Lake City, Utah
KLUKER@xxxxxxxxxxxxxxxxxxxxxxx


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