Transparency: Black fonts on empty background

[Cande Andrade]

Hi all,

After spending a few hours looking through forums unable to find answers, here I am asking the question:

For this show I am working on I am projecting black text against white background. The text is animated and will be projected on to 3x2 ft white screens.

I want to save tech time resizing or adjusting each cue but also want to avoid the white light from the projector  beaming every time text comes up. So I am trying to export my video files as animation to preserve transparency.

Of course, when I play the clips on my computer, the background reads black so I can't see the text. I wonder if once I play the files with QLab, the fonts will come up on the white screens, without me having to create a white background for every single one of the cues.

Any thoughts? Thanks!

Cheers
C

[mackerr]

Huh?

How do you think this gets rid of the white projector beam? There is no such thing as projecting black, only projecting a hole in the white. If you don't want to see the beams, keep the air clean or use rear projection.

Mac

[Jeremy Lee]

You could try inventing "Anti Light"

http://www.physforum.com/index.php?showtopic=6372

Jeremy Lee

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[Christopher Ashworth]

Hi Cande,

On Nov 14, 2012, at 7:27 PM, Cande Andrade <sols...@gmail.com> wrote:

> Of course, when I play the clips on my computer, the background reads black so I can't see the text. I wonder if once I play the files with QLab, the fonts will come up on the white screens, without me having to create a white background for every single one of the cues.
>
> Any thoughts? Thanks!

Think of a projector as something that will show the exact same thing as you see on your screen -- just project it.

Thus, if you see all black on your screen, you will also get all black coming out of your projector.

Best,
Chris

[Lucas Krech]

All a projector is is a fancy light source. You need some value greater than zero (i.e. not black) in order to see anything.

If you want a stark black and white look without a lot of illumination from the projector you may have better success with your projection surface being black or dark grey and your text being white. If you want the screens to read as white then you will need white light.

-L

Lucas Benjaminh Krech

Lighting and Video Artist

www.lucaskrech.com

646.263.8439

Vimeo.com/LucasKrech

Twitter: lucaskrech

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[Cande Andrade]

Thanks, everyone.

Chris, you got it. I was wondering if the transparency would be read through the projector.

I understand there is always light coming out hence the use of dowsers... I am just trying to avoid white "backgrounds"... the conundrum is that the text needs to be black. Aside from the fact that I will have to be resizing and fiddling with it a lot... oh text!

Cheers
C

 I guess I wasn't clear. I know there is always light coming from the projector. Though blasting a

[Cande Andrade]

Thank you Lucas,

I wanted the text to be white, though the set is all white. That's why I thought, well, in theory, if the fonts are black against a transparent background I should be ok to project over white. As Chris pointed out, I guess it doesn't matter if I encode the clips as animation, the projector is going to read the transparency as a black background regadless...

Thank you,
C

[mackerr]

It doesn't sound to me like you ARE getting it. Projectors work by projecting LIGHT onto a surface. Where you want black, nothing is projected. If the text is black, nothing is projected on that area. If you also want nothing projected on the rest of the area, it is all black. It is only the projected light around the black that defines it as the image you are projecting.

If you don't want a white background, pick another color. It just can't be the same color as the text if you want to see the text. Transparency has nothing to do with it.

Dowsers are used because video black is rarely if ever truly black. Some light leaks through the LCD panel/CRT/oil pan so you see a dimly lit box that covers the whole projection area. When that is unacceptable you use a dowser to kill all the light. 

Mac

[Cande Andrade]

Hi Mac,

Thank you. I guess my question was a bit confusing or wrongly framed. Bottom line: I need to create black text that will be projected on to white set. I thought (silly me) that creating the text on a transparent background and exporting with an animation codec would do once things needed to be projected.

Cheers!
C

[sam kusnetz]

you cannot project black text onto a white set. or in fact, at all. you cannot project black anything.

you could try black text with a white outline. but if the lights are up, the set will look white and there's nothing you can do to make it look black.

turn off all the lights in the room, and make an image that's fullscreen white with black text on it. that will bathe the whole set in white light except for the area covered by the letters. if the projector is the only source of light, it will have the basic effect of black text on a white set.

cheerio
sam
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sam kusnetz, sound & projection design | USA-829
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s...@notquite.net

[Daniel Perelstein]

I also think that the original poster has another misunderstanding about the process. Take the black vs. white business out of it. Let's say that your set was a brick wall and you wanted to project green text onto it, if I understand correctly, you couldn't do that. The projector can't only throw light into a custom region and nowhere else (unless it could be focused ... for instance if you wanted to project a green rectangle that'd be possible, but not an entirely custom geometry). If I understand correctly, the projector necessarily projects something onto the entire area that it's focused to cover.

Think of it like an overhead projector — the darn thing projects that rectangle, and you can put things onto that rectangle so that it projects those shapes, but you can't get the projector to project an image bound by a custom shape (for instance the text you want to project).

And, to further connect the dots that other folks have put up in response to this thread, but that I think haven't landed for the original projector, this is all tied to the question of a dowser — if you could have the projection geometry be customizable, you could just, when you want it off, make the projection area indefinitely small. But since you can't change the shape of the projection geometry itself, you've got that ugly rectangle that you have to dowse if you want it to disappear.

Taking this one step further, I'm envisioning controlling that projector geometry by use of an iris or something. So, you could iris in to focus down to a pinpoint instead of dowsing. Similarly, you could project your text onto the white background of the set, if you wanted to and it was a static, by putting for instance, a cardboard cutout of the text you want to read in front of the lens (I don't have an intuition for this stuff strong enough to know if that's the whole of it — there might be other factors including rotations and scaling to consider) and then putting a solid color slide into QLab. Nothing would project in the custom-dowsed area (i.e. it would achieve the "transparent" effect you're looking for) but you could get your solid color in the shape of the text.

Just thinking out loud here. I don't know a thing about video / projections or anything much in the visual world, but once upon a time I was a bangin' geometrist. :)
Dan

Daniel Perelstein                 

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[Angus Turner]

Basically a digital projector is the same as an overhead projector in that the way it projects stuff over the whole area. Instead of the yummy warm yellow of the lamp you get a 'black'. Which isn't really black. So you would be able to project green text onto a brick wall, but if it was in the dark you'd notice a slight rectangle where the projector stops projecting 'black' and real black takes over. If that makes any sense.
Thanks
Angus Turner
angus...@gmail.com

[mackerr]

You absolutely CAN project a custom shape. In your OH projector scenario try covering the table with a sheet of cardboard with a star cut out of the center, what have you got?

Projecting any color text but black is easy. It is BLACK that has no light where the text is. Green text, or red, or white all can be projected without lighting up the background, beyond a slight glow that whould not be visible except in a blackout.

From another end of the spectrum there is pixel mapping like is done with Pandora or M-Box. This lets you create custom projection shapes to match scenery or unusual screen shapes.

What the OP seems to be missing is that projected black is the absence of light. It looks no different than any other lack of light.

Mac

[Lucas Krech]

I *think* the custom shape post was largely a semantic point about the perpetuity of video bloack.

FWIW, and getting back to the OP, I have found that projecting plain white when dealing with text or simple geometry to be the most effective solution. Even though the literal thing is white light (whatever THAT means) the aesthetic experience is much closer to reading black text on a white page. The other benefit of white (or really as bright as you can get) against video black is that it becomes harder for the viewer to distinguish the edge of the projection thus mitigating one of the chief annoyances with projectors.

-L

Lucas Benjaminh Krech

Lighting and Video Artist

www.lucaskrech.com

646.263.8439

Vimeo.com/LucasKrech

Twitter: lucaskrech

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"What I give form to in daylight is only one percent of what I have seen in darkness."  

~M.C. Escher

[Mike P]

>
> What the OP seems to be missing is that projected black is the absence of light. It looks no different than any other lack of light.

I _think_ the OP has been trying to say in his last couple of posts that he now get's why it doesn't work.

RE: Custom Shapes. Do it all the time. Generally I use folded Blackwrap (tm) applied to the projector around the lens as a masking for unwanted light. This produces a very soft edge to the mask which is often beneficial in a lot of this work.

If you need a sharp edge, you may have to create a mask at some distance from the lens. This is tricky and can produce much bounce light from the back of the mask that can be distracting depending on how the projector is hung. We needed to create an irregular sail shape for a show about pirates and the mask wound up about 3 feet away from the projector suspended independently. This meant it was much larger due to the beam spread and since the projector was hung over the audience, we had to go back and create a blind from duvetyne around the area between the lens and the mask. The resulting rig was not aesthetically pleasing, but the image was great and it was easy to ignore the large black mass over the house.

Mike Post
(601) 307-8657
mdp...@mac.com
http://mdpostdesign.com