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Everything You Need to Know About Chroma Key and Green Screen Footage

The rapid development of cheap video processing technologies leads to the fact that many began to shoot with the help of chroma key backgrounds and in order to make the right choice of the background for shooting, they constantly ask the same questions to specialists. Here are the 10 most pressing questions about chroma key backgrounds that we have collected so that there are no more blank spots in this matter.


Why green background?


Look at your clothes, notice what the people around you are wearing. Green is rarely found in clothing and accessories, especially since it practically does not occur in the color of human hair and skin. Therefore, when you cut out the background from the resulting picture - photo or video during post-processing, it will be easy for you to tell the program that it is necessary to cut out the green color and replace it with the desired picture.

Do I have to use a green background?


Chroma keys may be in different colors. But in 90% of cases, green is used. The exception, perhaps, are the tasks in which it is necessary to shoot something based on Peter Pan, when he flies in a fairyland in a green suit. Under such conditions, you will have to choose a different background color for the chroma key. It's obvious why.

The next most popular chroma key for video shooting is blue and cyan, the third is bright red.

Photographers often use a regular white background to further replace the background. But it's still easier for photographers - they can sit longer over processing one frame, not to mention the fact that even a blonde in a white dress can be photographed against a white background so that it is easy to detach the background from the subject.


But to shoot a video, you will have to specially stock up on a color chroma key. Once, to shoot a film where it was necessary to close the stands of a hockey stadium, the assistant director was looking for an inexpensive background, as it required a large amount of it and turquoise. It is turquoise. As a result, I had to buy up a year's supply of non-woven background in this shade.

When creating special effects, Hollywood originally used a blue, matte color. The reason for this is simple: blue is the farthest color in the visual spectrum from red (which is the primary color in human skin tones.) This particular effect dates back to the 1940 film The Thief of Bagdad (which won an Oscar for its use of this effect). But in the modern world more often we can see the green colour of the background in spite of it being green.

Why? Today's cameras (camcorders in particular) have digital sensors that are very sensitive to green color. And yet, human skin tones do not contain blue or green, which prevents any background interference. (Just make sure your model is not from the planet Pandora!)

Any green background - chroma key?

There is no accepted standard on this issue. Any plain background can be used as a chroma key. 

A chroma key can mean a solid color of absolutely any shade or some kind of royalty-free picture. (Yes, there is more than royalty free music)There are some nuances: the green chroma key can be both light and dark, which is often indicated in the article. Depending on how the photophone was painted at the factory that day, the tone may differ with the same name. Therefore, even the best manufacturers should order a background from one batch. Although, for a post-processing program, semitone is not a disaster and there are no problems with further editing.


Do I need to highlight the chroma key?

Necessary. In the simplest case, when a person stands out strongly against a green background, and the lighting is diffused, there is enough light with which you illuminate the subject. But the right approach involves lighting a chroma key background. Illuminators can be located on top or on the side.


What's the best material?

Best of all backgrounds made of special low-crease, stretch seamless fabric with good reflectivity on the backing. This allows the background to be made in various shapes. Indeed, sometimes the background can bend around an obstacle or you need to hide something. But this is most often used for large projects in the film industry.

For a home or small studio, there are simpler options. The most popular option is a regular green fabric photophone. Its only drawback is that it is the most expensive of the three options and is very crumpled. By the way, wrinkles will be invisible with proper lighting.

The second option is a paper background chromakey. It's sleek, easy to light, but not easy to transport. It is difficult to drape a sofa in an apartment with a paper chroma key, and therefore is intended primarily for stationary use in a studio.

The third option is a non-woven chroma key background. Its main advantage is the price. It is not wrinkled as it comes on a cardboard tube. This background has fine perforations. But since the chroma key requires that the model be moved at least a meter away from it, the perforation is not visible and does not interfere with shooting.


Green reflexes appear on my face, what should I do?

Most often, a sufficiently bright green background with high reflectivity is chosen as a color key. A green background usually colors nearby objects green. Because of this, green reflections (i.e. highlights) are not uncommon on the cheekbones of a model or clothing. It's almost impossible to avoid this artifact entirely, but you can reduce reflections by powdering the subject's skin. The face will be matte, not shiny, and if you move the model a little further from the background, then there will be no green highlights, all the more so.


What size green background is needed for chroma key technology?

Everything just counts - the standard video size is about 2: 3. If you shoot a video horizontally, that is, when the width is 1.5 times the height, when you shoot a half-length portrait or the so-called talking head without legs, then the sweep will be about a meter plus fields (leave room for fields). You need a background of 1.6 meters minimum width, and preferably 2 meters. For a full-height one - 2.7-3 meters.


For video studios, the size is selected on an individual basis, and the owners of video studios usually do not have such questions - what width do I need the background for?


Practice in different locations and change your lighting, wardrobe, and props to see what effects you get. Import video into editing software and see how your video will look at different settings. And don't forget to record which video was shot at which settings. This will help in the future, already use your own ready-made settings.

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