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Exterior projector with alpha channel

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xdominguez pukkas
Exterior projector with alpha channel
on Jun 12, 2012 at 3:52:09 pm

My first post here, so be nice xop

Thing is: I need to make a projection on a display window so people on the steets can watch the videos. The video won't be projected to the glass, but to a adhesive semitransparent paper we will put on the window (don't know the name in english, I am from spain... It would be like a transparent vynil wall sticker).

I will create the video in AE, and probably export with Animation/Millions of colors+.

BUT: how will the image be viewed in plain daylight? Should I put some extra ilumination around the edges of the mentioned paper? About those edges, even if I make the video and it is perfectly seen, do I have to worry about any edge?


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Walter Soyka
Re: Exterior projector with alpha channel
on Jun 12, 2012 at 5:27:27 pm

[xdominguez pukkas] "I will create the video in AE, and probably export with Animation/Millions of colors+."

What device will play back the video?

There is no such thing as alpha in projection. Transparency in projection is achieved with black (no light).


[xdominguez pukkas] "BUT: how will the image be viewed in plain daylight? Should I put some extra ilumination around the edges of the mentioned paper? About those edges, even if I make the video and it is perfectly seen, do I have to worry about any edge?"

What effect do you want to achieve? If you want the edges to glow, yes, you will need some light there.

There are a few other challenges to consider.

You will need a very bright projector to overcome daylight -- and keep in mind that unless you build a tent around the projection cone, the projector's bulb will be visible to people off-axis.

As with all rear projection, there will be a hot spot in the line of sight from the viewer's eye through the surface to the projector.

Typically, rear projection uses a special material designed to reject light from the front in order to maximize contrast. You will probably have some serious contrast issues with retail glass and vinyl for projection.

I'd suggest you test your configuration somewhere before the install.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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xdominguez pukkas
Re: Exterior projector with alpha channel
on Jun 13, 2012 at 7:59:12 am

I am not sure what device are we going to get, this is what we want to achieve:

http://www.pantallasdeproyeccion.com/transparentes.htm

If you scroll down you will see a projection in a Nike shop.

As for the effect, I don't want any concrete effect for the projection. I asked about the edges because I've read this may be an issue when projecting.

What do you mean by building a tent around the projection cone?

Thank you for your answers.


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xdominguez pukkas
Re: Exterior projector with alpha channel
on Jun 13, 2012 at 10:27:09 am

Moreover, what do you mean by saying that alpha projection is achieved with black?


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Roland R. Kahlenberg
Re: Exterior projector with alpha channel
on Jun 13, 2012 at 12:26:19 pm

I believe Walter was trying to tell you that your design should include black areas to designate transparent areas in the projection. In post, we create a matte to denote transparency but in a projection environment, transparency is described by black pixels.

BTW, here are a couple of articles from Chris Zwar on building projections with AE - http://provideocoalition.com/index.php/motiongraphicsvizfx/story/an_a_to_z_...

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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xdominguez pukkas
Re: Exterior projector with alpha channel
on Jun 13, 2012 at 1:16:48 pm

Those videos look really helpful, I will give them a look when I have some time.

I understand what you mean with the black space, but if it is projected on an exterior window, won't the matte solid be projected as an extension of the animation I want to create?


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Walter Soyka
Re: Exterior projector with alpha channel
on Jun 13, 2012 at 1:44:23 pm

[xdominguez pukkas] "I understand what you mean with the black space, but if it is projected on an exterior window, won't the matte solid be projected as an extension of the animation I want to create?"

Consider projection like the Add blend mode in After Effects. The brighter a pixel is, the more influence it has in the composite. Intensity and opacity are intertwined.

Because black is no light, a projector shines no light in the black areas.

Of course, practically speaking, most projectors do not have an absolute black, but sunlight will likely wash out what little light may emit in the blacks. Alpha is meaningless to a display (it's only useful in compositing) so even if you do have high black levels, an alpha channel cannot help you. If you are using a 16x9 surface, this won't matter much anyway as the projector will be aligned to the surface.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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