courtesy  :  muo

What is green it screens ?

It’s not always possible to shoot videos and images in interesting locations with unique backgrounds. They could be far away or inaccessible. Or worse, nonexistent, like fantasy or science fiction settings.

But, that doesn’t mean creating videos with incredible backdrops is exclusive to big-budget studios. Thanks to green screens, everyone can be anywhere at any time in their videos. So, what are green screens, and how does a simple piece of green fabric create a whole new world?

What Is a Green Screen?

In the fields of photography and videography, a green screen is a backdrop of bright green canvas that allows photo and video editors to change the entire background later on in post-production. The goal is to make the transition from the location of the shoot to the edited backdrop as seamless and natural as possible.

Green screens are usually made of synthetic stretchable nylon spandex, but any bright green fabric can be used as a green screen—although with varying results. In fact, some people paint their walls a bright green color to mimic green screens.

Essentially, green screens act as a placeholder for the background. It’s the biggest indication that whatever is being shot is going to have an entirely different background.

But, Why Green?

The choice of green can feel a bit puzzling at first, but the answer is straightforward; people, and the majority of clothes, furniture, and decors, aren’t green. While green is a prominent color in nature, it’s rarely used in everyday fashion or decor, whether it’s a house, an office, or a coffee shop.

Other colors, such as brown, yellow, orange, and red can be found in various shades all around and even as undertones in people’s skin and hair. While it’s possible, when it’s time to replacing the screen with a background, those colors make the work ten times harder.

Green Screens vs Blue Screens

Blue is another color that isn’t often used in artificial objects and people aren’t blue. Not to mention, blue is the rarest color in nature, with very few animals and plants with any shade of the color.

So, Why Not a Blue Screen?

Various types of colors of “green” screens were used in the early to mid 20th century in black and white movies and plays, but they gained in popularity once digital cameras came around. Digital cameras tend to capture twice as much green color compared to all other colors, including blue. That means, it’s easier to single out and replace the green background in post-production than any other color.

Another reason is that green screens require less light to be bright, which means you’d need less lighting on your shooting set. Perfect for photographers and studios working on a budget.

The biggest disadvantage of green screens—which leads to the occasional use of blue screens—is also their brightness. There’s a lot of color spill onto other parts of the set. So, anyone or anything you’re shooting would have a green light reflecting on it. That’s especially a problem if you’re photographing shiny or reflective objects.

Blue screens are much easier to use when filming dark scenes, where there shouldn’t be much light. Also, they’re easier to key out around objects that melt into the green screen, like blond hair. Still, blue screens are more expensive to use as they need a lot more light to work properly.

How Do Green Screens Work?

In concept, green screens rely on a simple technique. But, in practice, small details and changes in light exposure can have a significant change in the quality of the resulting image.

When setting up the green screen, it’s important that the entire surface is uniform. That requires even and strong lighting and the canvas material to be as straight as possible with little to no wrinkles that create troublesome contrast.

You also need to be careful your actors or models don’t cast a shadow on the green screen by using overhead lighting.

What Is Keying?

Keying is the process of removing the green screen in post-production using photo or video editing software. After keying the background, you’d be left with a transparent background, where you can install anything—from images to videos that blend seamlessly into the main subject of the shot.

Chroma Keying

Chroma keying is the most common type of keying used with green and blue screens. It separates the image or video into layers depending on color hues. Every color has a unique chroma range, also known as the chrominance value.

With chroma keying, you can transform all areas of your image or video of this specific color into a transparent layer.

Luma Keying

Instead of operating on the basis of color, luma keying sets layer transparency based on the brightness or luminance level. Luma keying lets you add a semi-transparent foreground clip of the image over the base image that shows more in specific areas depending on the brightness.

While it can be used to overlay video for dramatic effects or smooth transitions, it’s most commonly used in editing still images.

Color Spill

Color spills occur when there’s too much light on the backdrop screen that it reflects on the objects or people you’re filming, acting as a colored filter. It’s more common with green screens compared to any other color of backdrop screen.

Most color spills are minuscule and can be ignored, especially if there aren’t reflective objects or clothing items. For mild cases of a color spill, affected edges and areas can be easily color corrected to eliminate or minimize the effects of the green screen.

What Comes After Green Screens

Green screens have been used in movies since the 1940s and still persist today. The bright green canvas is still the same. It’s the photography and keying technology that’s evolving with every new digital camera and video editing software.

Some high-budget filming studios are forgoing the green and blue screens altogether in favor of curved LED screens. However, green screens are unlikely to go away anytime soon as they’re cheap to implement and easy to use with the help of modern keying software.