P3D Re: Delurk, Projectors, EKTAGRAPHIC vs TDC-116

[wduggan3d@xxxxxxxx (WILLIAM A DUGGAN)]

On Thu, 5 Nov 1998 15:48:22 -0500 (EST) fj834@xxxxxxxxxxxxxxxxxxxxx (Dr.
George A. Themelis) writes:
>>With the limitation of 4" or 5" lenses and the need for frequent
>>adjustments, however, the TDC 116 is really not suitable for quality
>>projection to large audiences in my opinion.
>>William A. Duggan, APSA 
>
>Hi Bill!  Thanks for the projector information.  
>I have a couple of questions:
>
>- How would you define a large audience?  Is the typical stereo club
>  of 40-50 max people included in this definition?

DUGGAN REPLIES:  I would consider the TDC-116 OK for the typical stereo
club audience of up to 50 people max.  I consider large audiences to be
75 to 1000 people. How would you define large audiences, George? 
>
>- Why does the TDC 116 have a need for frequent adjustments while the
>  Twin Ektagraphic projectors do not (other than focus)?

Thanks!
>
>George Themelis
>

DUGGAN REPLIES:

The difference, assuming correctly mounted slides, is in precision in the
gate.  The TDC projectionist pushes slides into the gate from the side,
and these slides are somewhat loose.  Thicker mounts ride higher than
thin mounts.  The force of the operator in pushing the slide may cause
small variances in the final position of the slide.  There is no
mechanism to make sure that each and every slide ends up in exactly the
same position.  And as slides vary in thickness or thin slides warp,
refocus is frequently necessary in using any TDC model. The TDC is labor
intensive for the projectionist.

Twin Ektagraphic III projectors with the automatic focus button "ON" are
focussed manually for the first slide, and thereafter need not be
refocussed until a new tray is started.  In all EKTAGRAPHIC III
projectors, the side ramming mechanism pushes each dropped slide into
exactly the same position in the gate so that no adjustments are needed
for correctly mounted slides.  The projectionist need only align the
edges of the right and left frames (superimpose the two frames ) of the
first slide in each tray, and thereafter no adjustments should be needed
for correctly mounted slides.
After aligning and focussing the first slide of a tape-operated show, the
projectionist could go to lunch or take a shower and do something else
until the tray needs changing.

When slides are correctly mounted, they are mounted so that the
separation of homologous infinity points is NO MORE THAN 2 1/2" on a
given size screen when the frames are superimposed.  Thus, slides mounted
for a 6' by  6' stereo club screen would have a separation of 5"(causing
eye discomfort) if projected on a 12' by 12' screen at a convention, for
example, in which case the projectionist should not superimpose the
frames but would make a horizontal adjustment to bring the frames closer
together so that the separation would be no more than 2 1/2" .  Too often
this is not done at large conventions where large screens are used.  See
mounting instructions with the three mounting gauges sold by Reel 3-D.

George, why do you ask the above questions?.  You know more about
projection than I do.  What is your opinion???? 

William A. DUGGAN, APSA   wduggan3d@xxxxxxxx    and  wduggan3d@xxxxxxx
>
>

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