I went to see Borat with my folks–both in their fifities. They loved it. My mother put it in the top three movies of “embarrassing myself at laughing”.
(Borat wanders into the shot of a weatherguy at one point)
Was sitting with my dad watching a weather thing a few days later. And he asked “why do they do that in front of a green screen?”
(I went into a few things I a bit know about bluescreen and stuff–him: so, You don’t know?)
Him: why not a back screen projection and the weather person in front of it? (he reffed the Borat with the weather guy)
My WAG was that it’s put together digitally in a computer and and a real projection would be not have as much def as some computer thing.
Am I halfassed correct?
him: “well maybe”
The color that is used is done so because it provides contrast between the people in front of the screen and the background. If the screen was black, for example, you would run into trouble if someone was wearing a black shirt.
At the station I worked at in El Paso, the screen was bright orange.
The chroma-key (official term) can be any color the technical director decides it should be - as long as it’s dialed into the switcher console correctly.
And you’re absolutely right, a rear projection wouldn’t have the sharpness and definition of the digitally replaced picture. It’s been tried and rejected many times. A small rear projection, maybe. But the larger you need it to be, with weather maps and the like, the fuzzier rear projection gets. Chroma-key, on the other hand, stays sharp.
I’ve seen it happen when someone was wearing a flashy necktie. Bits of the background leaked through where the color of the tie matched the chroma-key color.
In addition to the sharpness problem noted by Rico you also have the issue that the stage & actor are very brightly lit. A rear projection screen would have to be bright enough to look bright even when flooded with very intense light. Not practical.
I’ve actually been meaning to ask this so I’ll piggyback it here. Is there some reason why the standard seems to have changed from a blue screen to a green?
They haven’t. In fact, it was Green Screen work back in the day, with sci fi movies and travelling mattes and whatnot.
Some of the sensitivity with film stocks opposed to video cameras/processors accounts for the changes in what most folks chose to use to key a shot. And, as has been mentioned, if the characters are clad in blue outfits, ChromaKey Blue ain’t gonna cut it !!!
As usual Wikipedia does a reasonable job of articulating the basics of how a Chroma Key works.
A neat side-note. Many folks thought that the Invisibility Cloak used in the Harry Potter films was a keyed effect, or digitally handled effect. In fact, I have held the device used to create this effect, and it is- incredibly-mounted ON the camera. Instead of needing a very flatly carefully evenly lit background for keying, this technology uses a ring of l.e.d.'s around the lens to shoot a specific light at a gray fabric of highly reflective properties.
It is an affect one sees in real-time on the video tap monitor of the film camera. Quite something, really. The folks who made this, and proved the brilliance of the technology, sell it to other production companies who wish to do on-site moving key shots.
Unbelievably, Invisibility Cloak technology is no longer sci fi stuff. Google " Invisibility Cloaks" to see. Jeeez.
When I was working in TV, blue was used for chroma key.
I think the main reason is that people tend to wear blue (and the blue that was used back then was a nice-looking blue), which means that the weather map might appear on your tie. People rarely wear green these days, and certainly not the gaudy, lime green of a green screen. So by switching to green, your on-air people don’t have to worry about clothing color.
It isn’t nearly as impressive as you seem to think. It’s extremely impractical; you need cameras and projectors set up and if you move, your equipment has to move with you. It looks pretty good in the publicity photos, naturally, which conveniently fail to show all the supporting equipment needed to accomplish it. I doubt it will ever amount to anything other than a novelty.
Blue screen is (was) used in film, and it relies on a different process than Chroma Key. In blue screen, a special film-developing process is used to produce a travelling matte in which the blue background becomes transparent and any foreground (non-blue) objects become opaque, and a reverse matte of this is also produced. One such matte pair is made for each foreground object to be included in the shot. The various travelling mattes and reverse mattes are used to block out areas in a background shot in which the new foreground objects will be inserted in a device called an optical printer to produce the final shot.
True- but what irks me is that the VERY COOL real photographic on-set trick developed by a British company for the live and very much moving shots in the Harry Potter films wasn’t something I could find Googling. So many pages dedicated to the kind of stuff you linked to is in the way. Their effect, which of course is not true invisibility, does not go away when the actor or camera moves. Of this I am quite sure, since in Denver at a trade show a few years ago, they mounted the Ringlight of l.e.d.'s on my Steadicam and I walked around someone wearing the matching reflectant cloak.
I’ve also seen amusing examples with the digital first-down lines and other markings they show on televised football games. Those are keyed to green, of course, since that’s what the grass is, which means that you used to sometimes see a first-down line digitally painted across a Packers or Jets uniform. I think they’ve improved the technology now so that doesn’t happen, though.
Way back when I worked in local TV in college, we used a rear screen for those shots over the anchor’s shoulder. The screen was only about 18" x 24" and was pretty much at the limits of resolution at that size. There’s no way it would have worked for something as large as a weather map.
We also keyed on blue, but our TV production instructor told us that at that time, CBS used green for the key color.
Can you please provide a little more detail on how this is supposed to work; the famous ‘invisibility cloak’ example that is all over the web works by projecting an actual image of the background onto the subject, but you appear to be describing something that projects just some kind of non-image-specific light on the subject. how would that make the subject invisible? or rather, how would that allow your steadicam to record things that are obscured by the subject?
Hmm. So Cartooniverse says the screen was and is green and Q.E.D. says it was or is blue. Now, I wasn’t talking about Chroma key on TV so that may be where some of the confusion lies.
Bluescreen was used in film until the Superman movies. They had to use greenscreen to differentiate his costume. It worked so well that it is now common to use greenscreen. Modern films are not composited in optical printers anymore as QED stated. Film is digitally scanned and the compositing is done in the computer.
Indeed. Sorry, I was addressing Keying as much as older travelling matte technology !
As for the question about the actual effect. Hmm. You drape this fabric over you. You look at the fabric through the camera. You see the fabric. You see the image on a monitor, and the fabric becomes a moving flexible keyable matte, into which you key whatever you want to.
In the case of the Harry Potter films, what was keyed into place is what was already in the shot. Quite easy, and rather amazing to see when it happens someplace outside of an effects suite in a post house.
So, this means that you still have to already have a shot of the background without the cloaked person there, right? What advantage does this offer over just making the cloak a constant color (green, or whatever), and using a more traditional chromakey or matte?
