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Light masking with a video projector - suggestions?

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Michael Sirois
Light masking with a video projector - suggestions?
on Apr 11, 2013 at 2:24:26 pm

Hi Creative Cow!

I am working on video content to be projected onto a clear screen. The video is of a person standing still and it is meant to be like a "holographic" assistant. I was thinking about cutting a human size frame out of frosted screen material to project onto. Ideally I would want the person to be the only light projected but that seems to be a very complex task. Instead, does anyone know of any masking alternatives? Apart from using tape or similar material to create a custom mask? I was trying to research into whether there was software or hardware designed for this, but unfortunately there didn't seem to be a lot of discussion about it.

Thanks!

Michael J. Sirois | Filmmaker & Musician


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Mark Suszko
Re: Light masking with a video projector - suggestions?
on Apr 11, 2013 at 4:46:49 pm

The guys on the Live and Stage forum would probably be of more help, but yes,I've seen such stuff done for point of sale displays or trade show eye-catchers, as greeters in airport concourses...

http://www.tensator.com/us/showroom/tensator-virtual-assistant.aspx







(these look a little creepy to me)


...and of course one of the best peppers' ghost type projection illusions is down here in Springfield, IL at the Lincoln Presidential Library and Museum.








You don't specify if this effect is to be experienced on a location by a live audience, or if you're just wanting the illusion of a hologram appearing in an otherwise conventional video. To give better advice, we really need to know which effect you mean to do: the live one on a stage setting in public, or inside of a regular video.

The live one IS harder to do well. The tensator version uses a very strong clear plastic cutout in the shape of the virtual person, with their elbows tucked in. Any overshoot by the projector hits only air, and the relationship between the projector lens and screen cutout are fixed. If you instead use a taut, stretched-out screen in a frame, the virtual presenter can move their arms more naturally. That's what was used for the virtual tupac








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Michael Sirois
Re: Light masking with a video projector - suggestions?
on Apr 11, 2013 at 6:44:36 pm

Thank you for the response!

Tensator's productions are actually what I am basing this project on, so basically the same thing but a cruder DIY version. I plan on using this in a live environment to display during a conference event. I thought about Pepper's Ghost but that seems unnecessary. I will be using rear projection but I don't believe a mirror is necessary. I will use Photoshop to create an outline of the assistant's body after I film, chroma key and remove the background. Then I will scale the outline to match the exact height of the assistant model and cut an outline using clear rear projection film with a frost tint so that the light doesn't completely pass through. I will also probably have to adjust the brightness to enhance the effect. Maybe I will just use black gaffe tape to cover up the areas on the projector lens where I know no content will be (other than the black background in the video).

How does that sound?

Oh, and I was going to use a DLP projector for higher contrast with "ultra short throw" distance and at least 2000+ ANSI lumens, unless someone has a better suggestion as to which projector to use.

Thanks again!

Michael J. Sirois | Filmmaker & Musician


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Mark Suszko
Re: Light masking with a video projector - suggestions?
on Apr 11, 2013 at 7:15:09 pm

Gain, ask the pros that do this in the live and stage forum, but I'm always happy to give an opinion, even on things I have no expertise in:-)

And that opinion is, don't bother making the custom human-shaped surface, and don't add any diffusion to it.

Instead, make a simpler, thin panel of mylar or your rear-projection material, in a banner shape. I vote for the thin mylar, the edges will be harder to spot. Disguise it first with the projection of a banner, and have two REAL sister banners in the scene as well, hung from above with invisible thin steel wire or monofilament. Anchor all three banners to the floor so breezes and drafts don't bend them.

Next, pre-warp the final comp to counter extreme keystoning, then the projector can hide on the floor or in the ceiling/rafters, very near the screen, instead of on a table or tripod "behind" the illusion, yet visible to all. Since the projection is projecting UP-wards, or nearly vertically DOWN-wards, any spill is not aimed at the viewer's eyes, thus not perceived. I would keep the projector on the floor and bounce it off of a small mirror: it makes setup, access and adjustment, and hiding the projector easier.

The fake banner dissolves into the virtual person on cue.


Please Do run my crazy notions past the experts in that other forum first, as I may have missed something.


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Michael Sirois
Re: Light masking with a video projector - suggestions?
on Apr 15, 2013 at 3:52:52 pm

Thanks again for the quick response! I really appreciate the help and it has been useful. I am going to try out a few of these ideas and see what happens. :)

Michael J. Sirois | Filmmaker & Musician


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Mahesh Sureka
Re: Light masking with a video projector - suggestions?
on Jan 3, 2014 at 3:50:45 am

I was wondering whether this idea would work properly. But I will try as an system integrator we want to install cut out of politicians before election. If anyone come with better idea, please let me know.
Mahesh Sureka, Director, Shree Satguru Infocom P Ltd , India


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