Re: Dissolves for 3-D projectors

[SCHUB@xxxxxxxxxxxxxxxxxx]

    It seems to me that there's no need to design a custom dimmer circuit--
the dimmers used in the light-boards of theaters should do the job nicely,
and are already designed to handle a large load.
    But a low-tech solution also occurs to me--it's something I saw in a
photo of an old double-magic-lantern setup.  You leave the bulbs at their
usual brightness and dim the projectors by moving a graduated neutral-density
filter in front of each projection lens.  You just attach the two graduated
neutral-density filters to the ends of an arm that's pivoted in the middle,
such that when you tilt the arm, you increase the filter density in front of one
lens while decreasing the density in front of the other.  In the old
magic-lantern setup, the whole thing was just a single piece of sheet-metal 
that formed both the arm AND the graduated neutral-density filters--the filters
were sort of shaped like a salad-fork, so that when just the tines are in front
of the lens, very little light is blocked, but as you put more of the fork in
front of the lens, the taper of the tines means that more and more light is
blocked.  Does that make sense?
                                                Martin Schub


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