A projected image is all about contrast. Nothing on this STH billboard, or in a movie theater, can appear "less dark" than the ambiance, only "more bright".
Not only is a movie theater darker than your average game room but (and here's the kicker) the image takes up most of your field of view. As a result your irises adjust to the average lumens the same as they would on a bright beach or a dark cave. Darth Vader/Batman is really white (no light transmitted, the base screen color) but because everything else is much brighter your eyes "scale" the dynamic range and presto - they look black.
This doesn't work on a small projector with a limited brightness and throw. The image is a small % of your field of view and therefore peripheral "light pollution" make the dynamic range of the projector look very narrow. Even if you play in the dark with no other games it's still competing with the insert lights, GI, LCD and backglass.
The concept is great. Pinball is a static medium and being able to "paint" different things onto objects is an awesome idea. But to really do it right you'd need a "real" projector, you know spend $400 maybe on it, which would require mounting it at a right angle below the PF near the coin mechs, using mirrors to turn the light 90 degrees to shine onto the playfield. (That's all more expensive than just a Pico under the apron) Then you'd have to deal with bulb life, heat dissipation and fan noise that would make a Spooky pin sound like Helen Keller.
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