Re: Eclair Cameras: beam splitting

[Wade Ramsey <wramsey@bju.edu>]

> Reading in my trusty guide to low budget filmmaking, I encountered a chapter on special effects using a beamsplitter. I said, "Should talk to the guys on the list about this one," realizing that I had said it out loud on the subway, I pretended I was on a cell phone. Since I was underground, it was a bad scene.

But, hey, what can you do? Does anyone know about where to get a beamsplitter and how double exposure works with them? 
Larry<

The type beamsplitter used for this is a semi-reflecting mirror.  It's what we used for front projection, years ago.  It transmits about 80% and reflects about 20%.  Other percentages are available, such as 50/50, but it doesn't matter much.

You place the mirror in front of the lens at a 45 deg. angle so that what it reflects is superimposed over what you can see straight through it.  By adjusting the illumination on the side subject you can establish how much of a ghost image it creates over the straight ahead view.  

This way you could super art work to the side of the camera over a scene straight ahead, for example, maybe you have a scene that needs sunbeams streaming through high windows, but you don't have xenon spots to create them.  Paint the beams on the artwork and super them into place.

An even more complex setup could utilize mattes.  Use a black matte to block out the top of the mirror so it only reflects what's to the side; the bottom is unobstructed so you can see through.  This way you could matte an artwork ceiling over an incomplete set.

Then there's front projection.  A projector is set up at the side of the camera so its beam bounces off the mirror toward the set.  Behind the subjects in the set is a reflex screen (Scotchlight) that will reflect the projector's beam right back at the camera, which sees the combined scene through the mirror.  This was a very effective means of matting backgrounds in, especially for 16mm, where blue screen wasn't an option and digital effects hadn't yet been invented.

Or you can cross dim the two subjects to create an in the camera dissolve between two scenes.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614

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