P3D Re: Projector manipulation?

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

In p3d digest 3744 Dr. T. writes:

> Sorry, I don't understand the problem.  Please explain.  Why
> using a mix of mounts results in projector manipulation?  What
> kind of manipulation?

Horizontal, vertical, and focus.

A good example comes from Ken Luker in p3d digest 3745:

> But then 
> I found that both green and blue heat-seal mounts were 
> susceptible to quality control problems:  the bottom edge 
> of the cutout, and therefore of the window, was not exactly 
> parallel to the bottom edge of the mount, so the mounted 
> pair was viewed or projected with a slight rotational 
> displacement of the window (one window edge was lower 
> than the other)  That could be fixed in projection by 
> adjusting the vertical, but in a viewer it was uncomfortable. 
> And projection using more than one batch of mounts 
> required repeated adjustment.  

Not all mounts have the same dimensions. This is especially true of 
many European mounts. Dr. T. I am sure you have noticed this in 
the overseas folios you participate in. I have never seen a wider 
selection of mount types and sizes. This includes the spacing of the 
aperture windows which cause the greatest problem with horizontal 
alignment.

Different mount thicknesses call for much great focus adjustment. 
Go from an EMDE aluminum mount in an aluminum stiffener to an 
RBT mount and see how much you have to crank that focus knob on 
a TDC.

Placing a Spicer in an EMDE binder with glass raises the whole 
thing as compared to a plain Spicer. If I have adjusted my projector 
to fit the screen with a plain Spicer, then when I project one in glass 
the top will be cut off.

I know many of these may seem like small adjustments and petty 
complaints, but attend a projected show some time with all the 
slides mounted in identical mounts and see how smoothly it goes 
with only an occasional slight adjustment to the focus. Compare that 
to a showing of an exhibition where every other slide is mounted 
differently. One of two things will happend. Either the projectionist 
will be constantly adjusting the vertical, horizontal, and focus to 
provide the best, least uncomfortable view possible or there will be 
no adjustment and the audience will have to suffer with unfusable, 
out of focus, or misaligned images.

That's all for now,

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