question: Why do some greenscreens look painfully obvious and lower quality than others?
comment: A myriad of reasons ranging from a poor camera setup and staging/lighting of the green screen plates to limitations of the vfx software/compositor skills in pulling a decent key of the foreground object. There are relighting/edge blending issues that also have to be addressed when combining the foreground fill/matte and background plates to achieve a high-quality result.
passages: The central tools of the List Translator are the GreenScreen Specified Lists and the GreenScreen List Translator Map. 
   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 the green screen and the Green Goblin had to be shot in front of a blue screen. The color difference is because Spider-Man wears a costume which is red and blue in color and the Green Goblin wears a costume which is entirely green in color. 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 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.
  
  Section::::Background color.
   The main challenge of greenscreen shooting is neither technical (though it does take forever) nor financial (it’s still less expensive than shooting in space). No, the main difficulty is in the acting. More specifically, the “black hole gaze”. Usually visual cues such as ping pong or tennis balls are used to focus the actor’ eyes on their virtual partners. But no tennis ball can do justice to the wonder, fear and humility such a spectacle should evoke. It takes a lot of discipline and imagination from the actors and absolute accuracy in the direction to pull off. The "black hole gaze" was the focus of many rehearsals, often up until a few seconds before shooting each of those shots.
   If the foreground object was filmed close to the backing screen or with less than ideal lighting conditions, the foreground object will usually have ‘spill’ somewhere on it. This is most common when filming blonde people against a blue or greenscreen as their translucent hair will absorb the backing screen color. Such ‘colorspill’ can be removed and replaced with several options to achieve a more realistic result.
   The biggest challenge when setting up a bluescreen or greenscreen is even lighting and the avoidance of shadow, because it is best to have as narrow a color range as possible being replaced. A shadow would present itself as a darker color 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. 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 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 color range. In order to get the cleanest key from shooting greenscreen it is necessary to create a value difference between the subject and the greenscreen. In order to differentiate the subject from the screen, a two-stop difference can be used, either by making the greenscreen two stops higher than the subject, or vice versa.
   The GreenScreen List Translator is the first step in a GreenScreen Assessment. It is also used as a stand alone screening protocol by health and sustainability screening and certification programs. It is widely referenced in standards and certifications related to green building products, including the Health Product Declaration Standard (HPD), Portico, and the "Building product disclosure and optimization - material ingredients" credits in the US Green Building Council's LEED program.
  
  Section::::External links.
  
  BULLET::::- GreenScreen for Safer Chemicals home page for the GreenScreen Standard
  
  BULLET::::- Clean Production Action publisher of the GreenScreen
   A studio shot taken in front of a green screen will naturally have ambient light the same color as the screen, due to its light scattering. This effect is known as "spill". This can look unnatural or cause portions of the characters to disappear, so must be compensated for, or avoided by using a larger screen placed far from the actors.
  
  Section::::Process.:Major factors.:Camera.
  
  The depth of field used to record the scene in front of the colored screen should match that of the background. This can mean recording the actors with a larger depth of field than normal.
  
  Section::::Clothing.
   Just before principal photography was about to begin, the company purchased a pair of workstations dedicated to 3D graphics and enhanced their Avid mounting system. The film was shot in ten days, with a Sony HVR-Z1. The bluescreen technique, which involves acting against an otherwise blank backdrop with backgrounds filled in later, was used for all the scenes with Prati, done at Illusion's studios. The technique spares the production the cost and time of constructing a physical set, but, as Prati pointed out, it also means the actor has no points of reference.
   Sometimes a shadow can be used to create a visual effect. Areas of the bluescreen or greenscreen 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 color will make the result look unnatural. A difference in the focal length of the lenses used can affect the success of chroma key.
  
  Section::::Tolerances.:Exposure.
   BULLET::::- LT-UNK (List Translator Benchmark Unknown) - Listed only on a list that does not meet or overlap Benchmark 1 criteria.
  
  BULLET::::- NoGSLT (No GreenScreen List Translator information) - Not listed on any of the GreenScreen Specified lists
  
  BULLET::::- NoGS (No GreenScreen information) - Not on any of the GreenScreen Specified lists and there is no public Greenscreen full assessment.
   Episodes that have been made with the games starting with "Halo 3" have used the theater mode camera. The Forge Mode from "Halo 4" onward also helped by providing a green screen and the creation of entire areas for certain scenes.
   An LT-Unk, No GSLT or NoGS score is not an indication of low hazard or safety for a substance, only that the substance has not been listed for the priority health endpoints. A full GreenScreen Assessment must be undertaken to determine if the substance qualifies as an affirmatively safer substance. 
  
  Section::::Automation.
   Green screen (disambiguation)
  
  Green screen compositing, or more generally chroma key compositing, is a technique for combining two still images or video frames.
  
  Green screen may also refer to:
  
  BULLET::::- Green-screen display, a monochrome CRT computer display
  
  BULLET::::- GreenScreen Interactive Software, a publisher of video games
  
  BULLET::::- Green screen of death, a failure mode on the TiVo digital video recorder and Xbox 360 console game system platforms
  
  BULLET::::- Green Screen film festival, a film festival in Germany
  
  BULLET::::- GreenScreen for Safer Chemicals a green chemicals assessment tool.
   The web presenter technology involves using a green screen backdrop when filming so that the video can be edited using Chroma key compositing. This allows the video to appear as a transparent overlay onto any website using a single line of HTML (and often javascript) code. A green screen is used as the image sensors in digital video cameras are more sensitive to green than any other colour.
   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 a reasonable match. For outdoor scenes, overcast days create a diffuse, evenly colored light which can be easier to match in the studio, whereas direct sunlight needs to be matched in both direction and overall color based on time of day.
   Scott avoided using green screens unless necessary. Instead, he used various items so the actors would know where they should be looking in any particular scene on the practical sets where CGI elements would be inserted in post-production. Rapace said that green screens were used fewer than six times during filming. The production used five 3ality Technical Atom 3D rigs, four of which were configured with Red Epic 3D cameras set on camera dollies and tripods, which were continuously in use during filming. The fifth rig used an Epic camera as a steadicam, which was used only occasionally.
  
  Section::::Production.:Post-production.
   The GreenScreen standard is developed, maintained and published by Clean Production Action (CPA), a non profit organization, based in the United States. CPA publishes the GreenScreen as an open standard which anyone can utilize. To make a public claim using a GreenScreen Benchmark, however, the GreenScreen assessment must be completed by a Profiler licensed by CPA.
  
  Section::::Related standards.
   Section::::Garbage and holdout mattes.
  
  A "garbage matte" is often hand-drawn, sometimes quickly made, used to exclude parts of an image that another process, such as bluescreen, would not remove. The name stems from the fact that the matte removes "garbage" from the procedurally produced image. "Garbage" might include a rig holding a model, or the lighting grid above the top edge of the bluescreen.
   In an episode of "Coronation Street" in 2010 an editing error meant viewers could see "outside" via No. 5's (Fiz and John Stapes' house) kitchen window showing what would be a "supporting" wall (quite possibly the painted brick wall backdrop) leaning against the studio walls. In another episode where Graham Proctor announced his relationship to Tina McIntyre's ex, David Platt, a brief shot of the Platts' kitchen showed no ceiling above it. It is not the first time such errors have occurred: in one episode where Alan Bradley attacked Rita Fairclough, viewers could see a studio light in what should be No. 7's back yard.
   It is commonly used for weather forecast broadcasts, wherein a news presenter is usually seen standing in front of a large CGI map during live television newscasts, though in actuality it is a large blue or green background. When using a blue screen, different weather maps are added on the parts of the image where the color is blue. If the news presenter wears blue clothes, his or her clothes will also be replaced with the background video. Chroma keying is also common in the entertainment industry for visual effects in movies and video games.
  
  Section::::History.
  
  Section::::History.:Predecessors.
   For the Sky Tower set (built on a soundstage in Baton Rouge), Kosinski and cinematographer Claudio Miranda worked closely with visual special-effects house Pixomondo to establish both environment and lighting by the use of 21 front-screen projectors aimed at a huge wraparound backdrop to form one continuous image, rather than blue screen backdrops. The backdrop consisted of a single seamless piece of painted white muslin, , which was wrapped around the set for 270-degree coverage. This enabled the full environment to be captured in camera, and assisted in lighting up to 90 percent of the set.
   Another challenge for bluescreen or greenscreen is proper camera exposure. Underexposing or overexposing a colored 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 a bright and saturated image.
  
  Section::::Programming.
  
  There are several different quality- and speed-optimized techniques for implementing color keying in software.
   Executive producer Bob Sertner wanted the film to have higher-end special effects to mimic the quality of those seen in feature films. To do this, the film uses visual computer effects created by special effects company Area 51 FX, which created over 100 different shots using the digital modeling program LightWave 3D. During shooting, special effect supervisor Craig Weiss noted that the scenes with Randy Quaid were particularly difficult to capture on film due to his appearing in multiple scenes where his character was chased by twisters and surrounded by their destructive aftermaths. The actors also faced new challenges, as the film often replaced traditional green screen setup, where the special effects were added during editing, with live shots taken with the effects in place at the same time. Nancy McKeon, who was pregnant with her first child during production, filmed some of her scenes using a green screen. She found the experience to be fun, noting that it challenges actors to use their imaginations while performing. She also found it easy to play a television reporter due to her being a self-admitted "news junkie."
   Section::::Process.
  
  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 color are replaced by the alternate background video. This process is commonly known as "keying", "keying out" or simply a "key".
  
  Section::::Process.:Processing a green backdrop.
  