Chroma is a tool essential in film production, television and advertising, as it allows creators to bring to life otherwise impossible worlds and characters. In this article we will explore what chroma is, how it works and what can be achieved with this fascinating technique.
Definition and meaning of chroma
The chroma technique, also known as ‘keying’ or ‘chroma key’, consists of removing a solid color of an image or video to replace it with other content. Generally a green or blue colored background is used that is easy to separate from the rest of the image.
In this way, you can replace the original background for other content, such as a virtual stage or a real landscape, achieving impressive visual effects in films, television series, advertising content and videos in general. The chroma technique is an essential tool in audiovisual production and allows creators to bring to life worlds and characters impossible to create otherwise.
How is a chroma created?
To create a chroma, certain elements and steps. Here’s a brief explanation of how to create one:
Background: A fund should be prepared uniform and solid color, usually green or blue. This background can be a cloth, a paper, a painted wall, among others.
Lightning: It is important to adequately illuminate the colored background so that it is as uniform as possible, avoiding shadows and areas with different shades.
Recording: The scene or image with the solid color background is recorded. It is important that the objects or people to be overlay on image do not have colors that resemble the background.
Edition: Video or image editing software is used to separate the color from the background and replace it with other content. For this, a tool called ‘keying‘, which allows you to select the color to remove and adjust the threshold values for optimal separation.
Overlap: The desired content is added to the replaced colored background, be it a virtual stage, a real landscape, or a computer-generated character. It is important adjust scale and position so that the overlay looks natural and realistic.
What kind of green is chroma?
The type of green used in chroma is known as ‘chroma green’ or ‘screen green’ and is a bright, saturated green which is used as a uniform background for removal in post-production.
Chroma green is chosen because it is a color that is not found in most of the objects and clothing used in the scene, allowing for easy separation from the background. Also, green has a wavelength that makes it easily distinguishable from other colors, making it a good choice for the removal process in post production.
What can be done with a chroma?
Chroma is a post production technique that allows to create visual effects and scenarios for audiovisual production. It is very versatile and you can do many things with it, such as creating virtual scenes, changing the backgrounds of recorded scenes, add special effects and within the area of education you can create educational content. In photography, this technique can also be used to create surreal or fantastic scenes.
In addition, chroma is widely used in the film, television and advertising industry, as it allows for a great flexibility in post production, which saves time and money. The actors can act on a simple set and the background can be added later in post-production. This is especially useful when you want to recreate scenarios that would be expensive or impossible to build in reality.
The use of chroma has also given rise to new opportunities in the video game production and virtual reality. Virtual sets and characters can be created in a studio and superimposed on real images to create a visually stunning experience. A notable example is the video game series ‘Uncharted’ by Naughty Dog, which used chroma to create the game’s environments. The developers created a physical set for the actors and used chroma to add the virtual sets in post-production.
Another example is the game ‘League of Legends’ from Riot Games, which uses chroma to create the virtual backgrounds for the characters. Instead of having to build physical sets for each character and stage, developers can use chroma to create them in post-production, which save time and resources.
Finally, we have Fortnite, which also uses the chroma technique in some aspects of its audiovisual production. For example, the fortnite events Live often use chroma to add special effects and create virtual sets in real time. Players can see and experience the virtual settings as they play, which adds a extra dimension to experience of game.
What difficulties does the chroma have?
Although chroma is a very useful and versatile technique, also presents some difficulties that make its use more difficult. Here are some of the main difficulties associated with chroma:
Lightning: One of the most important difficulties when using chroma is lighting. Is essential illuminate properly the chroma to obtain a uniform background free of shadows. If the lighting is not adequate, spots can appear in the chroma background, which makes post-production difficult.
Background uniformity: For the chroma to work correctly, it is necessary that the background is uniform and without textures or shadows. If the background is not uniform, it can produce unwanted effects in post-production, such as the appearance of shadows or halos around characters or objects.
Use of green or blue clothing: To use chroma, it is necessary that the actors or objects that you want to overlap have a green or blue color. This can be difficult to achieve, as green or blue clothing can not be suitable for the scene or the characters.
Post production settings: Sometimes it can be difficult to adjust the chroma in post so that it blends seamlessly with the rest of the scene. It is necessary adjust brightnesscontrast, and saturation so that the chroma is properly integrated into the scene.
Reflections and shadows: Often objects or people placed in front of the chroma can create reflections or shadows in the background. These items can be hard to remove in post production and can affect the final quality of the chroma.
Movement of objects or people: The movement of objects or people in front of the chroma can be a significant challenge for this technique. If there is too much movement, it can be difficult to get a smooth background free of shadows or reflections.
Difficulty combining elements: If you want to combine different elements with the chroma, such as special effects or animations, it can be difficult to get all the elements to integrate properly and they look natural.
Technology limitations: The quality of the chroma can also be affected by the limitations of the technology used. For example, some camera devices may have trouble capture fine details or the sharp edges needed for good chroma.
How do you edit a chroma?
Chroma editing is a process that is performed using a video editing software that has the ability to work with layers and alpha channel, such as Adobe Premiere, Final Cut Pro, DaVinci Resolve, among others. To edit a chroma, the following steps must be followed:
Video clips are imported with the chroma background and the elements that you want to add. Next, the chroma background and the elements that you want to add, such as images, videos or special effects, are placed on the timeline.
After the positions and scales of the added elements so that they integrate correctly with the chroma background. Likewise, the lighting and the background color chroma must be adjusted so that it integrates properly with the added elements.
Then they can add additional effects, such as blur or color effects, to improve the overall appearance of chroma. Finally, the final video with the edited chroma is rendered and exported.