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66-417: Compared to a silent stage , a sound stage is sound-proofed so that sound can be recorded along with the images. The recordings are known as production sound . Because most sound in movies, other than dialogue, is added in post-production, this generally means that the main difference between the two is that sound stages are used for dialogue scenes, but silent stages are not. An alternative to production sound

132-598: A "key". Green is used as a backdrop for TV and electronic cinematography more than any other colour because television weather presenters tended to wear blue suits. When chroma keying first came into use in television production, the blue screen that was then the norm in the movie industry was used out of habit, until other practical considerations caused the television industry to move from blue to green screens. Broadcast-quality colour television cameras use separate red, green and blue image sensors, and early analog TV chroma keyers required RGB component video to work reliably. From

198-480: A background from the subject of a photo or video – particularly the newscasting , motion picture , and video game industries. A colour range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as colour keying , colour-separation overlay ( CSO ; primarily by

264-427: A bright and saturated image. There are several different quality- and speed-optimised techniques for implementing colour keying in software. In most versions, a function f ( r , g , b ) → α is applied to every pixel in the image. α  (alpha) has a meaning similar to that in alpha compositing techniques. α  ≤ 0 means the pixel is fully in the green screen, α  ≥ 1 means

330-484: A chroma-key background and inserted into the background shot with a distortion effect, in order to create a cloak that is marginally detectable. Difficulties emerge with blue screen when a costume in an effects shot must be blue, such as Superman 's traditional blue outfit. In the 2002 film Spider-Man , in scenes where both Spider-Man and the Green Goblin are in the air, Spider-Man had to be shot in front of

396-463: A computer can use these markers to compute the camera's position and thus render an image that matches the perspective and movement of the foreground perfectly. Modern advances in software and computational power have eliminated the need to accurately place the markers ⁠— ⁠the software figures out their position in space; a potential disadvantage of this is that it requires camera movement, possibly contributing to modern cinematographic techniques whereby

462-416: A default value of 1.0. A very simple g () is ( r , min( g , b ), b ). This is fairly close to the capabilities of analog and film-based screen pulling. Modern examples of these functions are best described by two closed nested surfaces in 3D RGB space, often quite complex. Colours inside the inner surface are considered green screen. Colours outside the outer surface are opaque foreground. Colours between

528-446: A field monitor, to the side of the screen, to see where they are putting their hands against the background images. A newer technique is to project a faint image onto the screen. Some films make heavy use of chroma key to add backgrounds that are constructed entirely using computer-generated imagery (CGI). Performances from different takes can be composited together, which allows actors to be filmed separately and then placed together in

594-425: A filter or the high contrast film's colour sensitivity to expose only blue (and higher) frequencies. Blue light only shines through the colour negative where there is not blue in the scene, so this left the film clear where the blue screen was, and opaque elsewhere, except it also produced clear for any white objects (since they also contained blue). Removing these spots could be done by a suitable double-exposure with

660-460: A green screen and the Green Goblin had to be shot in front of a blue screen. The colour difference is because Spider-Man wears a costume which is red and blue in colour and the Green Goblin wears a costume which is entirely green in colour. If both were shot in front of the same screen, parts of one character would be erased from the shot. For a clean division of foreground from background, it

726-515: A green top to make it appear that the subject has no body), because the clothing may be replaced with the background image/video. An example of intentional use of this is when an actor wears a blue covering over a part of his body to make it invisible in the final shot. This technique can be used to achieve an effect similar to that used in the Harry Potter films to create the effect of an invisibility cloak . The actor can also be filmed against

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792-433: A narrow frequency band, which can then be separated from the other light using a prism, and projected onto a separate but synchronized film carrier within the camera. This second film is high-contrast black and white, and is processed to produce the matte. A newer technique is to use a retroreflective curtain in the background, along with a ring of bright LEDs around the camera lens . This requires no light to shine on

858-413: A new building specifically designed with the features and to bear the loads is required, which often is the less expensive alternative to retrofitting an existing structure because of engineering issues. Buildings without soundproofing still are referred to as silent stages and may be used where the dialogue and other sounds are recorded as a separate operation. This separate operation usually involves

924-420: A quarter of the time needed for other methods. In principle, any type of still background can be used as a chroma key instead of a solid colour. First the background is captured without actors or other foreground elements; then the scene is recorded. The image of the background is used to cancel the background in the actual footage; for example in a digital image, each pixel will have a different chroma key. This

990-463: A reasonable match. For outdoor scenes, overcast days create a diffuse, evenly coloured light which can be easier to match in the studio, whereas direct sunlight needs to be matched in both direction and overall colour based on time of day. A studio shot taken in front of a green screen will naturally have ambient light the same colour as the screen, due to its light scattering. This effect is known as spill . This can look unnatural or cause portions of

1056-483: A scene featuring a genie escaping from a bottle was the first use of a proper bluescreen process to create a travelling matte for The Thief of Bagdad (1940), which won the Academy Award for Best Special Effects that year. In 1950, Warner Brothers employee and ex- Kodak researcher Arthur Widmer began working on an ultraviolet travelling matte process. He also began developing bluescreen techniques: one of

1122-440: A technological perspective it was equally possible to use the blue or green channel, but because blue clothing was an ongoing challenge, the green screen came into common use. Newscasters sometimes forget the chroma key dress code, and when the key is applied to clothing of the same colour as the background, the person would seem to disappear into the key. Because green clothing is less common than blue, it soon became apparent that it

1188-403: A typical green/blue screen for chroma keying by displaying the solid color behind the performers. Having a physical space where actors can see their environment and inform their performances accordingly is something that most greenscreen sets lack. The controlled visual environment also allows directors and cinematographers the ability to better create mise-en-scène , with greater control over

1254-407: A white backdrop to include human actors with cartoon characters and backgrounds in his Alice Comedies . The blue screen method was developed in the 1930s at RKO Radio Pictures . At RKO, Linwood Dunn used an early version of the travelling matte to create "wipes" – where there were transitions like a windshield wiper in films such as Flying Down to Rio (1933). Credited to Larry Butler ,

1320-406: Is a stage that is surrounded (in varying degrees) by screens that extend the set. These screens, most commonly large arrays of LEDs , show a version of the set that was constructed in 3D (using software such as Unreal Engine ) that tracks its motion in real time with camera movement. A static display can function similarly for a still camera, given there is no parallax . However, these volumes allow

1386-405: Is achieved by a simple numerical comparison between the video and the pre-selected colour. If the colour at a particular point on the screen matches (either exactly, or in a range), then the video at that point is replaced by the alternate background. In order to create an illusion that characters and objects filmed are present in the intended background scene, the lighting in the two scenes must be

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1452-451: Is also important that clothing and hair in the foreground shot have a fairly simple silhouette, as fine details such as frizzy hair may not resolve properly. Similarly, partially transparent elements of the costume cause problems. Blue was originally used for the film industry as making the separations required a film that would only respond to the screen colour, and film that responded only to blue and higher frequencies (ultraviolet, etc.)

1518-496: Is best to have as narrow a colour range as possible being replaced. A shadow would present itself as a darker colour to the camera and might not register for replacement. This can sometimes be seen in low-budget or live broadcasts where the errors cannot be manually repaired or scenes reshot. The material being used affects the quality and ease of having it evenly lit. Materials which are shiny will be far less successful than those that are not. A shiny surface will have areas that reflect

1584-409: Is some use of the specific full-intensity magenta colour #FF00FF in digital colour images to encode (1-bit) transparency; this is sometimes referred to as "magic pink". This is not a photographic technique and the extraction of the foreground from the background is trivial. The biggest challenge when setting up a blue screen or green screen is even lighting and the avoidance of shadow because it

1650-437: Is sometimes referred to as a difference matte . However, this makes it easy for objects to be accidentally removed if they happen to be similar to the background, or for the background to remain due to camera noise or if it happens to change slightly from the reference footage. A background with a repeating pattern alleviates many of these issues, and can be less sensitive to wardrobe colour than solid-colour backdrops. There

1716-578: Is to record additional dialogue during post-production (known as dubbing ). Structures of this type were in use in the motion picture industry before the advent of sound recording . Early stages for silent movies were built, either as a three-wall open-roof set, or with large skylights, until electric lighting became powerful enough to expose film adequately. With the advent of electric lights, enclosed stages were built in Hollywood and rapidly converted to sound stages with many mattresses placed on

1782-458: The BBC ), or by various terms for specific colour-related variants such as green screen or blue screen ; chroma keying can be done with backgrounds of any colour that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from any human skin colour . No part of the subject being filmed or photographed may duplicate the colour used as

1848-407: The focal length of the lenses used can affect the success of chroma key. Another challenge for blue screen or green screen is proper camera exposure . Underexposing or overexposing a coloured backdrop can lead to poor saturation levels. In the case of video cameras, underexposed images can contain high amounts of noise , as well. The background must be bright enough to allow the camera to create

1914-622: The Wikimedia System Administrators, please include the details below. Request from 172.68.168.237 via cp1104 cp1104, Varnish XID 210737645 Upstream caches: cp1104 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 07:46:21 GMT Chroma key Chroma key compositing , or chroma keying , is a visual-effects and post-production technique for compositing (layering) two or more images or video streams together based on colour hues ( chroma range). The technique has been used in many fields to remove

1980-405: The actor in front of a blue screen together with the background footage, one frame at a time. In the early 1970s, American and British television networks began using green backdrops instead of blue for their newscasts. During the 1980s, minicomputers were used to control the optical printer. For the film The Empire Strikes Back , Richard Edlund created a "quad optical printer" that accelerated

2046-490: The amount of tedious rotoscoping work required in post-production to cut out what was not picked up by chroma keying. The downside to this setup is that unlike with greenscreen, whatever was filmed is final in terms of visual environment (as is the case with filming on any normal set or location). By contrast, a greenscreen film segment can essentially be swapped to anything at any point in post-production. Post-production Too Many Requests If you report this error to

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2112-453: The background other than the LEDs, which use an extremely small amount of power and space unlike big stage lights , and require no rigging . This advance was made possible by the invention in the 1990s of practical blue LEDs, which also allow for emerald green LEDs. There is also a form of colour keying that uses light spectrum invisible to human eye. Called Thermo-Key, it uses infrared as

2178-445: The background video. Chroma keying is also common in the entertainment industry for visual effects in movies and video games. Rotoscopy may instead be carried out on subjects that are not in front of a green (or blue) screen. Motion tracking can also be used in conjunction with chroma keying, such as to move the background as the subject moves. Prior to the introduction of travelling mattes and optical printing , double exposure

2244-459: The backing, or the part may be erroneously identified as part of the backing. It is commonly used for live weather forecast broadcasts in which a news presenter is seen standing in front of a large CGI map which is really a large blue or green background. Using a blue screen, different weather maps are added on the parts of the image in which the colour is blue. If the news presenter wears blue clothes, their clothes will also be replaced with

2310-478: The camera being more sensitive to green light. In analog television , colour 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 pre-selected colour. In-phase portions of the video are replaced by the alternate background video. In digital colour TV , colour is represented by three numbers (red, green, blue intensity levels). Chroma key

2376-452: The camera is always in motion. The principal subject is filmed or photographed against a background consisting of a single colour or a relatively narrow range of colours, usually blue or green because these colours are considered to be the furthest away from skin tone. The portions of the video which match the pre-selected colour are replaced by the alternate background video. This process is commonly known as " keying ", "keying out" or simply

2442-454: The characters to disappear, so must be compensated for, or avoided by using a larger screen placed far from the actors. The depth of field used to record the scene in front of the coloured screen should match that of the background. This can mean recording the actors with a larger depth of field than normal. A chroma key subject must avoid wearing clothes which are similar in colour to the chroma key colour(s) (unless intentional e.g., wearing

2508-445: The cleanest key. In the digital television and cinema age, much of the tweaking that was required to make a good quality key has been automated. However, the one constant that remains is some level of colour coordination to keep foreground subjects from being keyed out. Before electronic chroma keying, compositing was done on (chemical) film. The camera colour negative was printed onto high-contrast black and white negative, using either

2574-409: The colour positive (thus turning any area containing red or green opaque), and many other techniques. The result was film that was clear where the blue screen was, and opaque everywhere else. This is called a female matte , similar to an alpha matte in digital keying. Copying this film onto another high-contrast negative produced the opposite male matte . The background negative was then packed with

2640-410: The correct lighting for every shot. Television production generally uses multiple cameras, and cinema production generally uses a single camera. This is not universally true because the choice varies very much on what the director is trying to achieve. Rental of a sound stage entails an expensive process, but working on a sound stage saves time when setting up for production as long as access to all of

2706-422: The crew of a production to design and build the sets to exact specifications, precise scale, and detail. The art director of a production makes an architectural plan and carpenters build it. On a film, the head electrician is credited as the gaffer and the assistant as the best boy , regardless of gender. After a set is painted, the set dresser furnishes it with everything that the set designer , under

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2772-457: The direction of the art director , has selected for the interior. On a sound stage, the camera may be placed exactly where the director wants it. Achieving the desired lighting is easier because each stage has a metal framework with catwalks and lights suspended from the ceiling . This makes it easier for the cinematographer to have the grips position each flag or bounce and the lighting technicians to position each light to get exactly

2838-433: The female matte and exposed onto a final strip of film, then the camera negative was packed with the male matte and was double-printed onto this same film. These two images combined creates the final effect. The most important factor for a key is the colour separation of the foreground (the subject) and background (the screen) – a blue screen will be used if the subject is predominantly green (for example plants), despite

2904-514: The first films to use them was the 1958 adaptation of the Ernest Hemingway novella, The Old Man and the Sea , starring Spencer Tracy . The name "Chroma-Key" was RCA 's trade name for the process, as used on its NBC television broadcasts, incorporating patents granted to RCA's Albert N. Goldsmith. A very early broadcast use was NBC's George Gobel Show in fall 1957. Petro Vlahos

2970-427: The green channel. Green can also be used outdoors where the light colour temperature is significantly blue. Red is avoided as it is in human skin, and any other colour is a mix of primaries and thus produces a less clean extraction. A so-called " yellow screen " is accomplished with a white backdrop. Ordinary stage lighting is used in combination with a bright yellow sodium lamp. The sodium light falls almost entirely in

3036-414: The green screen two stops higher than the subject, or vice versa. Sometimes a shadow can be used to create a visual effect. Areas of the blue screen or green screen with a shadow on them can be replaced with a darker version of the desired background video image, making it look like the person is casting a shadow on them. Any spill of the chroma key colour will make the result look unnatural. A difference in

3102-423: The key colour, which would not be replaced by background image during postprocessing . For Star Trek: The Next Generation , an ultraviolet light matting process was proposed by Don Lee of CIS Hollywood and developed by Gary Hutzel and the staff of Image G . This involved a fluorescent orange backdrop which made it easier to generate a holdout matte , thus allowing the effects team to produce effects in

3168-431: The light starts blinking, it means shooting is in progress . Anyone who opens the door at that point will introduce external sound and light and ruin the take in progress. When a studio is home to multiple sound stages, they tend to all look alike from the outside: giant beige box-shaped buildings. Sound stages are marked on the exterior with large numbers to help distinguish them. An enclosed stage makes it easier for

3234-409: The lights making them appear pale, while other areas may be darkened. A matte surface will diffuse the reflected light and have a more even colour range. In order to get the cleanest key from shooting green screen, it is necessary to create a value difference between the subject and the green screen. In order to differentiate the subject from the screen, a two-stop difference can be used, either by making

3300-406: The listener's involvement in the recording, but also their overall perception of the stage. The latest technology and software can render basic previsualisation effects into scenes in real time while recording, before post-production , with the use of sensors detecting the position of actors and elements, in the staging of the frame. The director during filming can view what the composition of

3366-418: The necessary technical equipment, personnel, and supplies is readily available. As all the scenes can be filmed on the sets inside the sound stage, using it also eliminates having to move the production from location to location. With the use of bluescreen or greenscreen techniques (whereby backgrounds are inserted electronically behind the actors in the finished film) and a sound stage, extensive control of

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3432-403: The picture is with basic digital objects and surfaces included and how it appears, assisting the creative process. A newer form of set being used in both the production of films and television shows is the virtual production "volume". Different from the volume of a conventional motion capture stage (where often no physical image is being recorded for the final product), a virtual production volume

3498-439: The pixel is fully in the foreground object, and intermediate values indicate the pixel is partially covered by the foreground object (or it is transparent). A further function g ( r ,  g ,  b ) → ( r ,  g ,  b ) is needed to remove green spill on the foreground objects. A very simple f () function for green screen is A ( r + b ) − Bg where A and B are user adjustable constants with

3564-445: The principal actors doing synchronized dialogue replacement voice recordings over a working cut of the film, specialized language actors doing a secondary language dubbing or for the filming of special effects. A sound stage, unlike a silent stage, requires caution to avoid making noise anywhere within range of the audio recording equipment. A sound stage traditionally has a large red light above or next to each exterior door. When

3630-462: The process considerably and saved money. He received a special Academy Award for his innovation. For decades, travelling matte shots had to be done "locked-down", so that neither the matted subject nor the background could shift their camera perspective at all. Later, computer-timed, motion-control cameras alleviated this problem, as both the foreground and background could be filmed with the same camera moves. Meteorologists on television often use

3696-475: The production process is achieved. In audio recording , the term soundstage refers to the depth and richness of the recording, and usually relates to the playback process. According to audiophiles , the quality of the playback is very much dependent upon how one is able to pick out different instruments, voices, vocal parts, and such exactly where they are located on an imaginary, two- or three-dimensional field. The quality of this soundstage can enhance not only

3762-441: The same scene. Chroma key allows performers to appear to be in any location without leaving the studio. Advances in computer technology have simplified the incorporation of motion into composited shots, even when using handheld cameras. Reference points such as a painted grid, X's marked with tape, or equally spaced tennis balls attached to the wall, can be placed onto the coloured background to serve as markers. In post-production,

3828-483: The scenery to adaptively move and distort according to how the camera ought to see it if it were moving in a real environment. Benefits of such a setup include total control of a scene; dusk and dawn can last all day. Not only can time of day or number of light sources be manipulated at will, but portions of the volume off-screen can be turned completely white to add fill lighting from a given direction, or they can be turned off to darken that area. They can also function as

3894-408: The set, and the ability to see the final image as they are creating it. Where these volumes are especially beneficial is in having light behave perfectly realistically on transparent, translucent, and very reflective materials. These types of objects, such as eyeglasses, glassware, and shiny armor, are often very difficult to deal with in a conventional chroma key work flow. This technique also minimizes

3960-409: The surfaces are partially covered, they are more opaque the closer they are to the outer surface. Sometimes more closed surfaces are used to determine how to remove green spill. It is also very common for f () to depend on more than just the current pixel's colour, it may also use the ( x ,  y ) position, the values of nearby pixels, the value from reference images or a statistical colour model of

4026-405: The walls. With the coming of the talkies in the late 1920s, it became necessary to enclose and fully soundproof these stages to eliminate noise and distractions from outside, including limiting access. The ceilings and walls of the building containing the sound stage must be heavily soundproofed, so the structure must be sturdy and capable of accepting such additional features and loads, or

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4092-423: The window areas. In order to have figures in one exposure actually move in front of a substituted background in the other, a travelling matte was needed, to occlude the correct portion of the background in each frame. In 1918 Frank Williams patented a travelling matte technique, again based on using a black background. This was used in many films, such as The Invisible Man . In the 1920s, Walt Disney used

4158-410: Was awarded an Academy Award for his refinement of these techniques in 1964. His technique exploits the fact that most objects in real-world scenes have a colour whose blue-colour component is similar in intensity to their green-colour component. Zbigniew Rybczyński also contributed to bluescreen technology. An optical printer with two projectors, a film camera and a "beam splitter", was used to combine

4224-427: Was easier to use a green matte screen than it was to constantly police the clothing choices of on-air talent. Also, because the human eye is more sensitive to green wavelengths, which lie in the middle of the visible light spectrum, the green analog video channel typically carried more signal strength, giving a better signal to noise ratio compared to the other component video channels, so green screen keys could produce

4290-507: Was far easier to manufacture and make reliable than film that somehow excluded both frequencies higher and lower than the screen colour. In television and digital film making, however, it is equally easy to extract any colour, and green quickly became the favoured colour. Bright green is less likely to be in the foreground objects, colour film emulsions usually had much finer grain in the green, and lossy compression used for analog video signals and digital images and movies retain more detail in

4356-469: Was used to introduce elements into a scene which were not present in the initial exposure. This was done using black draping where a green screen would be used today. George Albert Smith first used this approach in 1898. In 1903, The Great Train Robbery by Edwin S. Porter used double exposure to add background scenes to windows which were black when filmed on set, using a garbage matte to expose only

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