Double Exposure Green Screen Video Download

When I had completed my double exposure on my friend, Me and and another student in our group thought it would be a great idea to make use of the green screen at hand to experiment with it. As can be seen by the featured image, it turned out really well as we took my green screened footage and keyed out the green leaving the desired footage ( unfortunately, my t-shirt included some green) The footage is again quite light-hearted and fun, but the way the footage lines up is good enough for me to call it a masterpiece.

My name is Garrett Sammons, a commercial director and cinematographer. In this next blog post, I will walk you through how to light for green screen and create a Hollywood-quality title sequence using compositing techniques.

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Green screen is a great tool to achieve an effect that would otherwise exceed your budget, set design, timeline, or other resources. Rather than needing to go out and film in a crazy environment or film a cool effect, you can add those things digitally in post instead. Green screen is also great for adding text to a shot or for achieving a double exposure or double composite.

There are a few basic lighting concepts to remember whenever you are lighting green screen, regardless of how you use it. When lighting for green screen, the first basic rule is to make sure you have even lighting across the entire screen. You need the background to be as evenly lit as possible. This ensures the chroma key is as even as possible and there is no unwanted shadows or light spill.

To achieve even lighting, you can use bright, large spread lights like the ones I used for this project. These lights also have adjustable settings that help you achieve certain effects with a green screen.

For our double exposure shot where our subject was wearing a hat, we had to modify this approach just a bit to avoid any harsh shadows from the hat. Here, we added a 48 bounce overhead and blasted our two Gemini 11 Hard lights up into the bounce. That created a very large, soft light source. We also placed our Astra 6X overhead as our edge light in the background. This helped us avoid any shadows from the hat on the subject.

So, having bright lights is extremely important. However, light evenness is also one of the most important factors when lighting for a green screen. You will need to create a very even light spread across the green screen to create an even key to create a crisp effect and reduce the work necessary in post.

Remember, the simplest way to get an even light spread and therefore an even key is to pull the lights away from the green screen. The closer the lights are to the green screen, the more focused the beam angle will be and the more uneven the light spread will be. Pulling both the lights and the subject away from the green screen surface will reduce green screen spill and create the most even lighting.

Lastly, to get a crisp effect and reduce the work needed in post, you need to avoid spill from the lights or green screen onto the subject. To prevent spill, you can set up flags between your light and your subject or between the subject and the camera.

If you follow these tips for lighting for green screen, then your foreground work and background work should flow together seamlessly and be believable. When you watch the final sequence, it should all blend so the viewer is unaware of the green screen or compositing.

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 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 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 the window areas.[5]

Petro Vlahos 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 Rybczyski also contributed to bluescreen technology. An optical printer with two projectors, a film camera and a "beam splitter", was used to combine 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 the process considerably and saved money. He received a special Academy Award for his innovation.

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 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 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 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.[10]

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 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 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 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.

In digital colour TV, colour is represented by three numbers (red, green, blue intensity levels). Chroma key 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.

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 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.

The biggest challenge when setting up a blue screen or green screen is even lighting and the avoidance of shadow because it 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 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 the green screen two stops higher than the subject, or vice versa. 17dc91bb1f