Talk:Chroma key

Untitled
redundant mention of weather map applications in intro paragraph and within article - Johnjosephbachir 01:24, 5 Dec 2004 (UTC)
 * I agree. I don't have time to deal with it now, but I added a cleanup tag. cluth 08:25, 5 February 2006 (UTC)

fact check for the History
The statement "Prior to the introduction of digital compositing, the process was a complex and time consuming one known as 'travelling matte'" does not appear to be completely accurate, however I need some help from someone with more expertise. By at least the 60s (maybe earlier) live TV shows used green screens (chroma key) in real-time, apparently using purely electronic video techniques, which I can imagine has something to do with detecting the part of the signal electronically that is the key color and merging a diff video signal into that part. It did not need ANY digital process, but was definitely not time-consuming or overly-complex for the operators of the live TV production (at least not any more complex than anything else production staff do real-time).

In summary, there are three assertions which are an issue in the above referenced statement...

1. Complexity: The context here, complex would be relative other editing technique. It was not complex as it was performed real-time by a live production crew on many shows on a regular basis at least by the 60s.

2. Digital composting: was not the first non-complex technique. (See above statement). This video chroma key was certainly was NOT digital composing (that should go without saying, the RAM required would have taken up a few buildings, ignoring the processing problem). It was a purely analogue electric signaling process.

3. Time Consuming: this is wrong in that Video based Chroma-key was around before digital, and the video technique not time-consuming at all... it was done in real time to a live audience.

Please editors let me know if you disagree or if you think I'm off my rocker. I shall revisit this article to clarify History at a later time. It will be tedious and take me a long time to create such content as I'm non-technical. Hopefully someone else jumps the gun before me!--Retran (talk) 09:05, 20 March 2010 (UTC)

There is the fact that the video chroma technique was not suitable for inclusion in motion film, the lines of resolution and interpolation in video wreak havoc when transferred to film. I doubt there was some way more advanced non-digital video technique/equipment with an extremely high lines of res, no interpolation, etc, comparable to film employed anywhere notable... but maybe there was? So the digital thing is probably the next step in reducing complexity and thus increasing availability of the technique... This makes makes me think the statement I have issue with in the article was referring to only motion-film. If so, maybe clarifying that point would be all we have to do for now to vastly improve the quality of this article.--Retran (talk) 09:13, 20 March 2010 (UTC)

I finally got rid of the "complex and time consuming" sentence. It was a bad start to the "History" section for many reasons. The history of composite shots neither starts with travelling matte, nor jumps straight to digital compositing. And travelling matte is not one process, it's something which can be done several ways as a part of several different processes. Some sources even refer to modern digital processes as using a "travelling matte". Dranorter (talk) 15:12, 9 June 2016 (UTC)

CSO
My knowledge (and limited research) shows that the term CSO is only used by the BBC, oither UK broadcasters use the term Chroma Keying (ITV for instance) --Jmptdc 13:35, 20 July 2006 (UTC) =: I agree. (I don't have a print source for this, but the subtitled commentary on my Doctor Who DVD tells me about it...) 72.147.60.53 02:42, 6 September 2006 (UTC)

Tags
The reasons for the inclusion of the tags will have to be discussed or they will be removed. --WikiCats 10:50, 20 September 2006 (UTC)

Picture?
This article really needs a picture. I'll try to find one, unless someone else already has one.

Jim Henson demo
I recall seeing a special on TV in the 80s on the making of the Muppet Show where Jim Henson and a (real) lion sat against a bluescreen appearing to be in a computer-generated room, and they switched back and forth between a composited and an actual view for demonstration. For further demonstration he put on a blue tie (which the background showed through). I think this was an excellent intro to the technology, especially for kids. I'd add a reference to the article, but can't remember enough details to cite it. I hope someone else might have better luck. Deco 17:12, 16 November 2006 (UTC)

Use in Australia - relevance?
Is the use of this technique limited to Australia, and if not why is this worthy of the article? The technique has been used in most broadcast news in most countries since the mid-late 90's. I'm removing this section. If anyone wants to add it back in with an explaination of WHY it is pertinant to the article please go ahead. The section removed read: Use in Australia National Nine News bulletins in Australia are always broadcast using the green effect background. At TCN-9, where the majority of national bulletins are broadcast, the same newsdesk is used for the morning news, afternoon news, the 6:00pm news and Nightline. Briefly in 2004, Seven News in Melbourne was broadcast with a shot of Melbourne in the background. This was used from August 2004 until mid-2005. Ten News in Adelaide is broadcast using the green effect background. The shot is of the Adelaide River with the Ten News logo in the middle. This version is actually broadcast in Melbourne to save on costs.

ASH1977LAW 15:39, 10 May 2007 (UTC)


 * Though Use in Australia is certainly not needed as a section, there is one interesting implication here: the article as it exists today gives no specific reason that news teams like to use blue screen. I didn't realize it was because they like to have a bunch of different-looking news desks for different things.64.186.47.170 (talk) 07:22, 7 June 2016 (UTC)

Advertisement POV
I removed this text from the "Even Lighting" section because it sounded like advertisement: Recently a much simpler and easier way to create an evenly lit background has been developed. By using screens made from a retroreflective fabric illuminated by a ring of LEDs around the camera lens it is possible to produce very even bright blue or green backgrounds whilst only consuming around five watts. Products such as Reflecmedia's Chromatte and LiteRing systems enable chroma key backgrounds to be created very simply and quickly, freeing the user to concentrate on lighting the foreground creatively. The systems are extremely energy efficient and enable users to create virtual studios in areas where space and energy are at a premium. I ran a check on the IP that added the text, 81.187.36.194, and it's registered to "REFLEC-PLC", the same company as Reflecmedia, the company mentioned in the text... Hmmmm... Interesting. Sbrools ( talk .  contribs ) 17:21, 2 November 2007 (UTC)
 * Good catch! --Ronz 18:57, 2 November 2007 (UTC)

Adobe Flash
Cant Adobe flash do greenscreen by making a background movie clip and making another layer with a different movie clip? Shouldnt this be mentioned in the article?71.53.20.131 (talk) 00:21, 5 December 2007 (UTC)
 * Flash can output files that include an alpha channel. This is created by simply recognizing areas that have no objects on them - there is no need to make special layers or background clips.  One would not call this "Chroma Key" however, because the alpha channel has nothing to do with the color of any object, but is instead is rendered from the geometry of files.  A rendered alpha channel is invariably superior to chroma key, because you don't need to worry about color ranges or reduced resolution of color channels.  You can also have transparent objects in the flash file allowing the background video to show through. Algr (talk) 07:03, 5 September 2008 (UTC)

Fair use rationale for Image:Utv cso studio.jpg
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BetacommandBot (talk) 05:13, 21 January 2008 (UTC)

paulscottfilms@yahoo.co.nz Paul Scott This discussion page seems far more technical than the article. I would say it is difficult to deal with a technical issuse like chroma key without use of specialised words, with exact meanings —Preceding unsigned comment added by Peterquixote (talk • contribs) 05:15, 27 April 2008 (UTC)

Racism
The articles says, many times, "human skin", "human skin colour", "human skin pigments", as if only white people were humans (as the article asumes human skin is pinky). I think this point of view is too whitecentric and must be fixed. --87.223.41.137 (talk) 13:42, 11 January 2010 (UTC)


 * While your concerns are noted, you are incorrect in assuming that the article is referring exclusively to Caucasian skin tones. I've added a reference that states "if the foreground is a person then blue or green backing color is recommended as these colors are not present in human flesh pigments. In fact, human skin color is 70% red for all people regardless of race.". I hope this helps to ease your concerns. --Ckatz chat spy '' 18:37, 11 January 2010 (UTC)

Programming
This section needs some work. The idea that a "program" processes the video on a pixel-by-pixel basis is naive. Earlier, with analog video, this was done using fast video switches. The two video sources had to be frame and line synchronous. The chroma key colored areas were detected with a phase looked loop (PLL). An example of an integrated circuit that could be used for this is the MC1378 by Motorola. Digital video chroma key operation is not programmatic either. A state machine, implemented in digital circuitry, is used. Zen-in (talk) 16:14, 19 October 2009 (UTC)

Is there a typo in the Programming section? It appears that

f(r, g, b) → K0 * b − K1 * g + K2

was originally intended to read

f(r, g, b) = K0 * b − K1 * g + K2 * r

Note (1) I added red to the last term (2) I changed the maps to sign (arrow) to an equality (=).

Am I right? --Hroðulf (or Hrothulf) (Talk) 18:02, 21 February 2010 (UTC)


 * No, the intention is that the last term is a constant and that the red value is not used in the calculation.Spitzak (talk) 00:13, 23 February 2010 (UTC)


 * Thanks Spitzak. In the article itself, I have inserted an equality (=) . --Hroðulf (or Hrothulf) (Talk) 14:59, 1 March 2010 (UTC)

Could someone please provide a reference for the example formulae? It would be nice to look at their derivation, but chroma keying gets very little discussion in the standard graphics textbooks. Michael Ashihkmin's paper is a very simplistic discussion (not to disparage its efficacy) and doesn't cover the formulae shown here. Cheers.Fluppeteer (talk) 15:47, 23 February 2010 (UTC)


 * The math is that used by the Nuke "Keyer" operator, which was implemented by reverse-engineering the keyer in Discreet Logic's Flame in 1995. In both cases these keyers are quite obsolete and do not make acceptable (to modern standard) separations, but the math is simple enough to understand and copy into an arbitrary program.Spitzak (talk) 20:58, 23 February 2010 (UTC)

The process fact check
The statement "Blue was used before digital keying became commonplace because it was necessary for the optical process" has some problems. It wasn't necessary because it was an "optical process", but the chroma key relied on masking chemically while developing film. And blue is one of the prim colors and the background change could be controlled chemically. This seems to be more accurately described as a chemical process, not an optical one (optical is too broad, yes it employs optics though so do digital). That's my non-technical understanding anyway. --Retran (talk) 09:30, 20 March 2010 (UTC)
 * Some clarity on this point would be nice, yes. My impression is: 1) Blue was apparently favored before the digital processes. 2) A "chemical process" was not involved. I thought at first there was some special "blue screen" film, a high-contrast monochromatic film using some specific chemical. However, I think what's going on is that a colored filter was used with black and white film when creating the matte. 3) Blue has a shorter wavelength and so is capable of a more detailed, accurate matte than green. I don't know if this makes a practical difference, but it may have been part of the decision, and is probably what a source means if it says blue could be high contrast more easily or could be more accurate.64.186.47.170 (talk) 10:28, 5 June 2016 (UTC)
 * After rereading the section I decided to delete the offending sentence. (As of today it read "Blue was preferred as a backdrop before digital keying became commonplace because of the existence of high contrast film that was sensitive only to the blue color.") It's making too strong a claim without a source, and the previous paragraph does a better job. Still, it would be nice to have sources verifying why exactly the blue color was popular; it seems like the technology for green screen basically existed. Another possible factor that comes to mind is the low luminosity of blue?64.186.47.170 (talk) 10:39, 5 June 2016 (UTC)

Really?
"This technique is also used in the entertainment industry, the iconic theatre shots in Mystery Science Theater 3000, for example."

MST3K is the best example of this being used in the entertainment field? —Preceding unsigned comment added by 76.185.84.11 (talk) 20:32, 22 June 2010 (UTC)

What Video camera?
Could a blue and green screen work on any video camera? —Preceding unsigned comment added by 98.71.53.3 (talk) 03:18, 2 May 2011 (UTC)
 * Yes, any color camera could work. However, the quality of the result would vary widely depending on the nature of the camera.  The worst case would be if the blue screen image was being played back from something like SVHS or Hi8, as these formats reduce the chroma resolution to well below what NTSC can do.  A camera with component out would be much better than composite.  The digital formats all keep chroma resolution reasonably high, and HD is a big help too. Algr (talk) 17:52, 31 December 2013 (UTC)

Green vs Blue and eye colour
The "Processing a green backdrop" section claims "Bright green has also become favored since a blue background may match a subject's eye color..." This is not cited, and does not appear to be factual. It implies that a green backdrop cannot match a subject's eye colour, which denies the existence of green-eyed people. Albertanyone (talk) 06:17, 30 December 2013 (UTC)
 * That seems unlikely. No one naturally has eyes that have nearly as intense color as the blue or green screens used in chroma key.  Algr (talk) 17:52, 31 December 2013 (UTC)
 * This point is overlooked in another context. As I understand it, keying is based not only on the hue, but on its saturation. A person could wear a light-blue shirt or dress against a backdrop of the same hue, without it causing problems. WilliamSommerwerck (talk) 23:37, 22 June 2014 (UTC)
 * I think this oversight is a significant one. Mostly what I came to the article for was to learn a little more about issues like this; is keying based on hue alone? How much variation in hue is allowed? etc. 64.186.47.170 (talk) 08:11, 29 May 2016 (UTC)

Ultimatte
I was looking for an article on Ultimatte. Wikipedia doesn't appear to have one.WilliamSommerwerck (talk) 23:42, 22 June 2014 (UTC)

major error
"In analog color TV, color is represented by the phase of the chroma subcarrier relative to a reference oscillator. Chroma key is achieved by comparing the phase of the video to the phase corresponding to the preselected color. In-phase portions of the video are replaced by the alternate background video."

This isn't true. Chroma keying occurs using the primary-color signals, long before they're manipulated to produce the NTSC or PAL subcarrier. WilliamSommerwerck (talk) 16:43, 6 July 2015 (UTC)

"Background" section
I removed the following sentence from the "Background" section, end of 1st ¶: "For example, in John Pizzarelli's song Birthday Emotions from the Sesame Street television series, painting backgrounds made by Gerri Brioso are used as a live-action film sequence while the kids such as the Italian-American siblings are jumping through the air and celebrating one of their birthday parties."

There is no reference given and the example is not particularly clear, and too detailed. It's supposed to be an example of red backdrops being okay.

That paragraph could use work overall. 64.186.47.170 (talk) 07:47, 29 May 2016 (UTC)

OK I removed another, more thoroughly irrelevant example, and renamed this section to "background color". — Preceding unsigned comment added by 64.186.47.170 (talk) 08:12, 29 May 2016 (UTC)

Removed "Citation Needed" from paragraph about Tosh.0. It's not a mystery or unfounded rumor. The green chroma key set is shown at the end of every single episode. — Preceding unsigned comment added by 8.36.244.10 (talk) 21:53, 28 May 2017 (UTC)

Bluescreen vs Chroma Key
I missed some points people made until a second read-through so I've decided to throw all the old merger discussion into one section. Assertions as to what Chroma Key technically means and how it's used seem to be all over the place. There is a little more back at Talk:Bluescreen. Dranorter (talk) 15:23, 9 June 2016 (UTC)

Arthur Widmer
Why is there no mention in any of the articles of Arthur Widmer, the inventor of BlueScreen? Seems none of the articles are complete, and so to merge at present would seem unwise/premature Rgds - Trident13 17:04, 4 June 2006 (UTC)

I disagree. It is true that none of the articles are complete, but attempting to rectify this in any one article would likely involve adding redundant information. IMO, it is preferable to merge the articles first, then begin to fill in the holes in the collective information. --IntrigueBlue 09:55, 30 August 2006 (UTC)

Merge with Bluescreen
I agree that Bluescreen should be merged into this article. --WikiCats 14:37, 6 September 2006 (UTC)

Bluescreen and greenscreen are types of chroma keying!

Yes, but they it is essential information. It should be merged, along with Greenscreen. --Ksong12 13:25, 5 April 2007 (UTC)

Yes, they should be merged. --24.238.178.85 21:39, 8 April 2007 (UTC)


 * Wait a minute: all these terms, in both film and video, relate to systems of compositing. That article needs work, though it's generally OK as far as it goes. Also, the static or traveling matte pre-digital film technology also used blue (or other color) background screens for compositing. I don't think we've yet found the top of the subject hierarchy here. Jim Stinson 03:35, 31 July 2007 (UTC)

Come to think of it, front and rear screen projection are forms of compositing, as are the glass shots used to combine action with painted set extensions on the original camera negative (The long road up to Ashley Wilkes' plantation in Gone With the Wind is a classic glass shot.) Jim Stinson 20:15, 31 July 2007 (UTC)

Merging bluescreen
I also agree that the article bluescreen should be merged into this, since bluescreen is a subset of chroma keying.

I am changing my vote on merging this article with bluescreen because Chroma key is about television and Bluescreen is about film. They should be separate but have references to each other. --WikiCats 10:50, 13 September 2006 (UTC)


 * It seems that the proposed merge has not yet happened, so I would also like to go on record supporting a merge of Chromakey, Bluescreening, and Greenscreening. IMHO, the merged article belongs under Chromakey.  Bluescreening and Greenscreening make sense as redirects to a merged article under Chromakey.  Bluescreening is not unique to film at all.  Chromakey with video does tend to use a green background instead of a blue one, but this is far from universal.  I've probably done very nearly as much compositing where I had to key out blue in video as I have with green.  The techniques and concepts are identical. Forkazoo 23:49, 26 July 2007 (UTC)

I think that they're the same thing, or at least so close that they could be covered accurately by a single article. I don't think anyone looking for information on one will be discouraged by information about the other being present in the same article. Gregory j 11:12, 20 September 2006 (UTC)

I agree that blue screen is a subset of chroma keying. There should be a section in chroma keying that talks about bluescreen as an application, while the search "bluescreen" redirects to the chroma keying article. zapp645 7:11, 19 October 2006

I think there is a certain amount of duplication between the two pages, but they are about (slightly) different topics. Bluescreening is the term known by most people so should remain active, even if only to site a reference to chroma-key. Alternatively how about Chroma Key (Bluescreening)? --A320sean 19:46, 18 February 2007 (UTC)

I agree that the two articles can be merged but wouldn't it make more sense to merge this article into bluescreen with a redirect from Chroma Key to bluescreen? After all, bluescreen is the larger of the two articles and this one could easily be made to fit into it. The subject matter is practically the same. I know that bluescreen is technically just a part of chroma keying but it is by far the more well-known term and so it would be easier for readers if that is where the information was as they would be more likely to search that one first. Silent Mime 23:27, 27 February 2007 (UTC)

But the point is that bluescreen is a subset of the chromakey as a function. So is greenscreen or other new reflective material screens. They should all be combined into the chromakey article and subdivided there into their respective subsets.

New compositing article
The use of blue screen (aka green screen and chroma key)in visual effects is included in the new article Compositing. Jim Stinson 22:58, 10 August 2007 (UTC)

Horrible Merger
Why has Blue screen been redirected to the out-moded term Chroma Key? Merging is a good idea, but merging from one specific term to another specific term, instead of a more general categorical term only adds inaccuracy. Chroma Key is a video only process that has gone out of favor for the most part. It certainly isn't used by the film industry and most video production artists today. Motion Image Compositing (or something else) would be a much better general term. --StevenBradford 22:18, 8 September 2007 (UTC)

Video versus Film
I understood that the term "Chroma Key" only refers to the VIDEO process of blue screen. The process for doing this is totally different when performed on video instead of film, and because of digital intermediates, the film version that is described at length is now obsolete. Doctor Who made extensive use of Chroma Key starting in 1970. -- Algr (talk) 19:07, 16 November 2007 (UTC)

Agreed. Chroma key is a video process. It is not an film process. These should be clearly separated into two articles. WilliamSommerwerck (talk) 23:34, 22 June 2014 (UTC)


 * What is the difference between video and film? It seems to me there is some need for one article about the various techniques which colloquially get called "blue screen" or "green screen" — that is, archtypically, techniques for making a person whose moving image is captured in the studio appear in the final product against a background which wasn't there in studio. Every technique which can accomplish this has some other uses too of course, but when people say "blue screen" or "green screen" that's what they're thinking of. Currently "green screen" redirects here to chroma key, and "blue screen" redirects to a disambiguation page leading to chroma key.
 * I realize a distinction can be made between video and film. And this article does, in places, need to be more specific about which techniques are chemical (ie, film) vs. optical (prisms, filters) vs. electronic vs. digital. (My impression is there was a stage during which electronic but not truly digital processing was state of the art?) "Chroma key is a video process" just seems a little beside the point to the average person actually seeking out this page.
 * We can't split hairs about what is and isn't chroma key. Nobody uses chroma key anyway. "Chroma key" as a technical term refers to chroma key as opposed to luma key or keying on any other dimension. Modern image compositing software is going to use chroma, luma, and other tricks to identify the backdrop. I don't have a good citation but if you google "not just chroma" you'll get quotes like "the newest generation of keyers are not just chroma keyers", "I think it's far more important that there be very robust controls on a keyer - hue selection, tolerance, edge tolerance and smoothing etc... And support for both luma and alpha channel keys are a must also, not just chroma key.", "they're not just relying on differences in chrominance (color), but also luminance (brightness differences) and other cool mathematical stuff that I can’t hope to understand."64.186.47.170 (talk) 05:00, 6 June 2016 (UTC)
 * Aha, here is a citation on the term "chroma key" almost always being abused in modern usage. The Green Screen Handbook: Real-World Production Techniques, by Jeff Foster; page 29. "The term chroma key is often used loosely to mean anything that refers to pulling a color-difference matte from film or video footage." (Bolding mine.) 64.186.47.170 (talk) 10:42, 6 June 2016 (UTC)

Terminology
There are several points where the article needs to take some care to be internally consistent with its terminology. I don't know enough to try and edit it all the way through. I realize there's no right answer on some of these, but consistency would be nice. Please feel free to edit my words beyond this point. Dranorter (talk) 15:57, 9 June 2016 (UTC)


 * "Blue screen" vs. "Bluescreen"? Bluescreen.
 * "Film" should be used as a verb only in sentences specifically referring to actual film. "Capture", "record", "shoot" seem more general.
 * Can "video" refer to film? I don't know whether this term is general enough to be used in phrases like the opening sentence, "technique for compositing (layering) two images or video streams together".
 * Can "footage" be used to refer to digital video? Is there a good alternative?
 * "Screen" vs. "background" vs. "backdrop".
 * Do we follow the convention some books use and call certain digital processes a "matte"?
 * "Movie" versus "film" - is "movie" an acceptable general term?


 * Bluescreen does seem to be used much more than Blue screen but think about it. Except for the color, Chroma Key using a Blue screen is exactly the same as Chroma key using a Green screen, right? So Bluescreen does not refer to something unique. Quite often people use terms without really thinking about them and you are trying to correct that and that is something I am likely to do but I think that Bluescreen requires more thought. Sam Tomato (talk) 01:26, 13 March 2019 (UTC)

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Blue screen, green screen vs bluescreen, greenscreen
Should these terms be one word or two? --Khajidha (talk) 12:08, 11 February 2020 (UTC)

Usage in video games?
The article twice states in the opening that chroma keying is used in video games, but does not elaborate or give any examples of this. The only games I could think of would be something like EyeToy: Play where it recognizes changes in pixels, but this doesn't really qualify as true chroma keying. Ethanicus (talk) 19:19, 18 February 2020 (UTC)
 * I suppose it could be used to produce cut scenes, or to use live action actors as part of a video game. But I agree this is not really used by video games, it is not used by any technology where the image is generated rather than photographed. Also "magic pink" was put in, that is a hand-painted color used to indicate transparent areas in sprites in very old games, it is not photographed and is has nothing to do with this either.

Rear projection
The section Predecessors should mention rear projection. A bit above on this talkpage, it seems somebody tried to argue against including rear projection by calling it "a form of compositing". But that's irrelevant as the function is largely the same: If you wanted to replace a background before the wide use of chroma keying (or as an alternative to it), you would often use rear projection. --46.93.152.142 (talk) 20:28, 25 May 2020 (UTC)