week 6- dinesh, kalai, kokila

Bluescreen is known as chroma key in television. Bluescreen is a term for the filmmaking technique of using an evenly-lit monochromatic background for the purpose of replacing it with a different image or scene. The term also refers to the visual effect resulting from this technique as well as the colored screen itself (although it is often not blue: for example, with greenscreen).

A chroma key is the removal of a color (or small color range) from one image to reveal another image 'behind' it. The removed color becomes transparent. This technique is also referred to as "color keying", "color-separation overlay" ("CSO") ,"greenscreen" and "bluescreen". It is commonly used for weather forecast broadcasts, where in the presenter appears to be standing in front of a large map, but in the studio it is actually a large blue or green background. A chroma key subject must not wear clothing similar in color to the chroma key color , because the clothing may be replaced with the background video. An example of intentional use of this is when an actor wears a blue covering over a part of their body to make it invisible in the final shot.

The principal subject is photographed or filmed against a background having a single color or a relatively narrow range of colors, usually in the blue or green because these colors are considered to be the furthest away from skin tone. When the phase of the chroma signal corresponds to the pre-programmed state or states associated with the desired color, the signal of the alternate background is composite and presented as the output. When the phase of the chroma signal deviates from the chosen color, the principal video is presented at the output. This process is commonly known as "keying", "keying out" or simply a "key".

Blue is generally used for both weather maps and special effects because it is complementary to human skin tone. However, in many instances, green has become the favored color because digital cameras retain more detail in the green channel and it requires less light than blue. Although green and blue are the most common, any color can be used. Occasionally, a magenta background is used.

With better imaging and hardware, many companies are avoiding the confusion often experienced by weather presenters, who must otherwise watch themselves on a monitor to see the image shown behind them, by lightly projecting a copy of the background image onto the blue/green screen. This allows the presenter to accurately point and look at the map without referring to monitors most difficult part of setting up a bluescreen or greenscreen is even lighting and the avoidance of shadow, because it is ideal 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 reflect light will be far less successful than those that do not. A plastic sheet will reflect light and have a hot spot in the center which will come out as a pale area, while the edges may be darkened. A cotton sheet will absorb more light and have a more even color range.

week 6- adriel,sarah,nicole

These days movies are not produced by just having a long cut acting shot but instead to make it interesting, people from the movie industry has since begun to use special effects to attract audiences' attention and hold it on for a very long time. By using blue screens which is known as chroma screens in television terms, these movie makers can do wonders to the effects they want to create. In the world of special effects now, chroma key allows one to film against a solid colored background and insert a desired background later. Special effects are basically any on-screen physical effect that is not done by the actor themselves. This can mean atmospheric effects such as smoke, wind, rain, haze or simulated conditions such as boiling pots, exploding cars or campfires.This also includes any movement of objects in front of camera such as falling dishes, floating furniture or breaking glass. One mundane example of the technique is the television news weatherman who on screen appears to point at a map. He is actually being recorded standing in front of a blank screen. On the sides of this screen are smaller televisions projecting a front view of the weathercaster, so they know where and when to place their hands.

Chroma Keys or Blue Screen is a term used often in the film making industry. It is a film making technique that allows the video editor to choose a color from a range of colors that become transparent. This is done by creating and using an even-lit monochromatic (having or creating only one tone of color) background to replace a different image or scene.

For example, the scene from E.T where Elliot and E.T rides on the bike that flies- blue screen is used. Although in reality there are strings attached to the bikes and other techniques are used, blue screen helps camouflage the strings attached and makes it invisible.

For blue screen technique, it is important that the lighting of the screen is absolutely even because fluctuations in intensity of lighting will cause the color or "key" to appear choppy or broken. For example, if the lighting for the E.T wasn’t set in the proper and even intensity, the strings attached to the bikes may be revealed in certain parts- causing the whole scene to be a flop.

Blue/green screens are also used in commercials as well. As commercials are becoming more animated so that they'll be able to sell their product or services, they are many things they won't be able to show without bluescreens. Directors for these commercials may want to do a commercial with a background that cannot be attained in real life, so they will describe to animators what background they want and these animators may then superimpose their background onto the bluescreen and have the actors or actressess act out their scenes. Actors would have to then imagine the background and act accordingly. Animated characters can also be put onto bluescreens by computers.

The bluescreen technique has been a most useful tool and the thing is that there are improvements yet to be made.

week 6- sam,daniel,sarah

Most movies nowadays that we watched on screens have special effects like The Matrix, Superman, Pirates of the Carribean and e.g.. The stunning display of unique environment and mind boggling effects could drop the jaws of any viewers who finds it fascinating. Of course though, most of the scenes in the movies are not real in reality because we know it is made up. The falling of a man into a massive ravine, or leaping from buildings to buildings are literally impossible but virtually possible. Now the question is, how did they made the special scenes come to real in the movies? They couldn't have actually screened a man leaping from buildings to buildings. Its just not possible because of the risk involved whether stunt-man or not. The not-so-secret secret lies in 'using green screens and blue screens' when filming these scenes.

There isn't any difference between green and blue screen actually. The methodology and techniques are the same. The illusion is created by a special effects technique known as traveling matte or blue screen. This technique allows actors and scale models to find themselves in totally imaginary situations -- in space ships, dangling from rope bridges over gorges, flying through the air (a la Superman) -- and have it look completely real in the theater. The technique is used so often now that you don't even realize it. News reporters are made to look like they are on location when they are not, and complete segments in TV shows can be created this way to make it look like the segment was filmed on location.

With computers, blue screen shots are even easier because the computer can create the mattes and combine the shots automatically. Many of the links on the next page describe different digital techniques.

The next time you go to a movie, you'll understand how they make some of these impossible shots -- but you can still be amazed at how real they look.

week 6 -gayetri,angeline,rana

Bluescreen is known as chroma key in television. Bluescreen is a term for the filmmaking technique of using an evenly-lit monochromatic background for the purpose of replacing it with a different image or scene. This also refers to the visual effect resulting from this technique as well as the colored screen itself (although it is often not blue: for example, with greenscreen).

Chroma key is the removal of a color (or small color range) from one image to reveal another image 'behind' it. The removed color becomes transparent. This technique is also referred to as "color keying", "color-separation overlay" ("CSO") ,"greenscreen" and "bluescreen". Commonly, Chroma Key used for weather forecast broadcasts, where in the presenter appears to be standing in front of a large map, but in the studio it is actually a large blue or green background. A chroma key subject must not wear clothing similar in color to the chroma key color, because the clothing may be replaced with the background video. An example of intentional use of this is when an actor wears a blue covering over a part of their body to make it invisible in the final shot.

The principal subject is photographed or filmed against a background having a single color or a relatively narrow range of colors, usually in the blue or green because these colors are considered to be the furthest away from skin tone. When the phase of the chroma signal corresponds to the pre-programmed state or states associated with the desired color, the signal of the alternate background is composite and presented as the output. When the phase of the chroma signal deviates from the chosen color, the principal video is presented at the output. This process is commonly known as "keying", "keying out" or simply a "key".

Although some colors can be used, blue is generally used for both weather maps and special effects because it is complementary to human skin tone. However, in many instances, green has become the favored color because digital cameras retain more detail in the green channel and it requires less light than blue. Although green and blue are the most common, any color can be used. Occasionally, a magenta background is used .

Now with better imaging and hardware, many companies are avoiding the confusion often experienced by weather presenters, who must otherwise watch themselves on a monitor to see the image shown behind them, by lightly projecting a copy of the background image onto the blue/green screen. This allows the presenter to accurately point and look at the map without referring to monitors most difficult part of setting up a bluescreen or greenscreen is even lighting and the avoidance of shadow, because it is ideal 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 reflect light will be far less successful than those that do not.

A plastic sheet will reflect light and have a hot spot in the center which will come out as a pale area, while the edges may be darkened. A cotton sheet will absorb more light and have a more even color range.

week 6- canaan,alvin,sim pin

Nowadays many movies use blue or green screens to create special effects. Most of movies use bluescreen and add background by using CGI (computer generated imagery). They use bluescreen to allows performers appear in any location in front of blue background without leaving the studio.

Soon after we edited it on the computer, we can move other features or element into it like earth background. So that they could appear to anywhere in earth, or any other world that could be appeared in real movies. Beside that, they also use the key backgound in the video signal. The video signal such as seperate camera, recorded video playback or digital sources is processed and overlaid with the key background.

Beside that,we can do chromakeying with any color on editing. But most of the time a pure blue or green are used because they are not present in human skin tones. Which color to use is something of a coin toss. Some folks claim that blonde hair keys better against blue. If we recording in DV format We found that green works just a bit better due to its higher luma content. The usual approach is to paint a wall with Rosco ChromaKey paint, which theoretically gives a pure color with little contamination from other locations on the color wheel. In my experience, though, we can just go to the paint store and get the purest green or blue they can mix. If painting a wall is impractical, for limited situations we can use blue or green cloth stretched as wrinkle-free as possible. In one show, we can even used green bulletin board paper from a local school supply store to extend the green screen onto the floor.

week 6- eric

Creating a blue screen composite image starts with a subject that has been photographed in front of an evenly lit, bright, pure blue background. The compositing process, whether photographic or electronic, replaces all the blue in the picture with another image, known as the background plate.

Blue screen composites can be made optically for still photos or movies, electronically for live video, and digitally to computer images. Until very recently all blue screen compositing for films was done optically and all television composites were done using analog real time circuits.

Another term for Blue Screen is Chroma-Key. Chroma-Key is a television process . The Chroma Key process is based on the Luminance key. In a luminance key, everything in the image over a set brightness level is "keyed" out and replaced by either another image, or a color from a color generator. Primarily this is used in the creation of titles. A title card with white on black titles is prepared and placed in front of a camera. The camera signal is fed into the keyer's foreground input. The background video is fed into the keyer. The level control knob on the keyer is adjusted to cause all the black on the title card to be replaced by the background video. The white letters now appear over the background image.

Chroma Key creates keys on just one color channel. Broadcast cameras use three independent sensors, one for each color, Red, Green and Blue. Most cameras can output these RGB signals separately from the Composite video signal. So the original chroma key was probably created by feeding the blue channel of a camera into a keyer. This works, sort of, but soon manufacturers created dedicated chromakeyers that could accept all 3 colors, plus the background composite signal and the foreground composite signal. This made it possible to select any color for the key and fine tune the selection of the color.

As keyers became more sophisticated, with finer control of the transition between background and foreground, the effect became less obvious and jarring. Today's high-end keyers can make a soft key that is basically invisible.

week 6 assessment

Write a one-page essay on how people use blue/green screens to create special effects in movies.