Placeholder Image

字幕列表 影片播放

  • [Class Assembling]

  • Hi! Welcome to FilmmakerIQ.com - I'm John Hess and today we'll explore Hollywood's

  • history of visual trickery with the backstory of modern greenscreen compositing.

  • With cameras and computers everywhere in our modern world, it's easy to forget that the

  • very first motion pictures were, themselves, essentially a special effect. It's here

  • at the beginning of filmmaking that we'll start our journey: the close of the 19th century

  • with one of the world's first prolific filmmakers - a man who spent his life studying the art

  • of illusion - Georgesliès.

  • In his 1898 film "Four Haads are better than one", Méliès employs a visual trick

  • that is the rudimentary beginnings of what we now think of as greenscreen compositing.

  • The use of mattes for multiple exposures.

  • Compositing is a technique combining different shots and elements into one image. The matte

  • shot was the first compositing techniques employed by early filmmakers such as Melies.

  • In his film, Melies would black out parts of the frame using a piece of glass with some

  • black paint. This "matte" made it so no light would reach the film so it wouldn't

  • get exposed. Then Melies would rewind the film and this time matted out of everything

  • else and expose only the part of the frame that was under the matte earlier. The resulting

  • double exposure could combine two or more different shots into one frame all done inside the camera.

  • This matte technique was used again on Edwin S. Porter's 1903 The Great Train Robbery

  • but this time not as magic trick but as a means to create a larger more realistic world

  • Notice the train moving outside the window of the train station - also the open door

  • of the mail car with the scenery in the background. Both of these shots were done using mattes and double exposure.

  • Now the fair question to ask here is why didn't they just shoot it in a real train station

  • or a real train car?

  • The answer is it was technically impossible at the time. Early orthochromatic film needed

  • a lot of light and the technology for efficient electrical lighting for film was still a decade

  • or two away. That's not even considering the inherent exposure problems of shooting

  • an interior scene with a window in the shot. Even modern day cameras have trouble with

  • the brightness differences between interiors and exteriors. In order to make film behave

  • they way we experience the world, visual trickery had to be done.

  • As film grew up in the 1900s and 1910s more techniques for augmenting sets and creating

  • false realities would be developed. The Glass shot was a technique of painting elements

  • on a piece of glass and placing that glass between the subject and the camera - a sort

  • of real world compositing which was refined by early filmmaker Norman Dawn, using it to

  • augment sets making them look much bigger and more elaborate without the costs of construction.

  • But the problem with the glass shot was the paintings had to be ready on set. Norman Dawn

  • solved this problem by painting the glass black and treating the shot like a matte shot.

  • The matted film would be transfer to a second camera where matte artists could take their

  • time creating the matte paintings. This matte painting concept continued seeing use in the

  • golden era of Hollywood and continues with us even in our digital world.

  • The problem with mattes is the camera had to stay perfectly still and no action could

  • cross the matte line - the "hopefully" invisible line between the live action and

  • the matte painting.

  • This is where the traveling matte came into place. The process patented by Frank Williams

  • in 1918 and demonstrated here in F.W. Murnau's 1927 film"Sunrise" - was a black matting

  • process which photographed subjects against a pure black background. The film would then

  • be copied to increasingly high contrast negatives until a black and white silhouette emerged.

  • This black and white silhouette was used as the matte - called a traveling matte because

  • it moved throughout the frame.

  • This "black back matte" effect which was called the Williams Process was used quite

  • famously by John P. Fulton in 1933 for the film "The Invisble Man". The shots where

  • the invisible man was taking off his clothes were accomplished by photographing actor Claude

  • Rains wearing a full black velvet suit standing against a black background. This effect was

  • so memorable and startling it was used on follow up sequels even after more effective processes came along.

  • The Williams Process had some issues - for one, any shadows on the subject would be lost

  • in the traveling matte. An alternative came about in 1925, invented C. Dodge Dunning which

  • would eventually be called the Dunning Process. This process used colored lights, lighting

  • a background screen blue and the foreground subject in yellow. Using dyes and filters,

  • the blue and yellow light could be split apart to create traveling mattes. The Dunning Process

  • would first see use on King Kong in 1933.

  • The problem with the Dunning Process was it only worked with black and white film. Color

  • Film needed a new technique and it would come in 1940 by special effects artist Larry Butler

  • in the Thief of Bagdad.

  • Using the three strip technicolor process, Butler shot the subject against a blue background.

  • Blue was used because it was the farthest away from skin tones and the blue film stock

  • had the smallest grain. Taking the blue separation from the three technicolor negatives, Butler

  • was able to create a silhouette matte just like with Williams process. Then, using an

  • optical printer, a relatively new invention at the time that could combine multiple film

  • strips into one, Butler would first remove the blue background from the foreground plate

  • and, using the negative of the travelling matte, remove the foreground space from the

  • background plate and then finally combining both foreground and background plates together.

  • This bluescreen technique won an Academy award for Best Special Effects for Larry Butler

  • in 1940 but it was not without its inherent problems. Firstly the process was extremely

  • time consuming as it involved several steps with an optical printer. Secondly, it still

  • had some edge issues where a thin blue line was almost always visible in the shots. It

  • also couldn't handle any fine details like hair or smoke or motion blur. Despite these

  • limitations, the blue screen process was used extensively including in such blockbusters

  • as The Ten Commandments in 1956:

  • Hollywood kept experimenting with other variations on the bluescreen process including the ultraviolet

  • matte as used in "The Old Man and The Sea". But the real challenger to blue screen was

  • created in the late 50s and credited to one of the giants in world of compositing Petro Vlahos.

  • Developed by Vlahos in the mid 50s and used extensively by the Walt Disney Studios in

  • the 60s and 70s: The Sodium vapor process used actors, who were lit normally, standing

  • in front of a white screen which was lit by powerful sodium vapor lights - those are the

  • orange lights you see on street corners. Sodium vapor emits light in a very specific wavelength

  • - averaging 589.3 nanometers - and nothing else.

  • Using a specially coated prism in an old three strip Technicolor camera, the very specific

  • wavelength of the sodium vapor light was split off and captured on special black and white

  • film - automatically creating the black and white traveling matte. The remaining light

  • would be captured by regular three strip Technicolor Film which was relatively unaffected by the

  • yellow/orange sodium vapor lights.

  • This technique produced some of the best travelling mattes of the time and was used by Disney

  • first on film The Parent Trap and then The Absent Minded Professor both in 1961. Mary

  • Poppins in 1964 demonstrated the capability of the sodium vapor process winning an academy

  • award for best special effects.

  • There was just one problem. Only One Sodium Vapor prism was ever made so there was only

  • one camera that was capable of this process. Disney owned the camera and they didn't

  • let it rent for cheap. Revenge of the Blue Screen

  • In the late 50s, When MGM was ready to produce Ben Hur in the MGM Camera 65 format (a 65mm

  • film process) they turned to Petro Vlahos, the inventor of the sodium vapor process for

  • help on the compositing. They didn't want the problems that Ten Commandments had with

  • bluescreen but The sodium vapor process wouldn't work as it prism it used was been made for

  • 35mm film, not 65mm. So Vlahos was asked to see if he could do something about trying

  • to improve the bluescreen process.

  • After six months of hard work, Vlahos had a discovery. And this is where it gets pretty

  • complicated. Most colors that aren't purely green or purely blue have about equal amounts

  • of blue and green in them. So when creating a matte from bluescreen, Vlahos used a Green

  • Cancellation separation (or positive), ran it though with the original color negative

  • exposing both pieces of film together under a blue to light to create a "blue difference

  • matte". This matte was clear where the blue and green were the same - Then the blue separation

  • positive was combined with the original negative and exposed under red light to get a cover

  • matte. This cover matte was applied back to the original color separations except that

  • the blue separation was replaced with a composite of the green and the green difference mask

  • - essentially a synthetic blue separation.

  • This complicated process required 12 film elements to get from the composite negative

  • to the composite internegative but it was remarkable in the way it single handedly solved

  • the edge and fine detail problems that plagued blue screen.

  • It was so successful in fact that the process remained in popular use for almost 40 years.

  • Developments like microprocessor controlled quad optical printers, employed by Richard

  • Edlund for The Empire Strikes Back made the process faster and more accurate but the next

  • big change to come would be in the form of digital.

  • I have consciously avoided the the term "chroma key" as historically the term applied only

  • to video systems only. That's not the case anymore. In rudimentary video mixers, a keyer

  • was a mathematical process that would make a range of colors in a video signal and make

  • it transparent. This is, of course, a common effect that television newsrooms all over

  • would use weather map special effects.

  • Blue as a screen color was still predominate but green started to take over as films began

  • getting the digital post production treatment in the late nineties. Why Green? Basically

  • Green was easier and cheaper to light than blue, green registers brighter on electronic

  • displays, worked well for outdoor keys (where the blue screen might match the sky) and the

  • bold green color was less common in costumes than blue is.

  • And now as digital camera are replacing film, many digital sensors use a Bayer Pattern which

  • have twice the number of green photosites than red or blue to capture luminance. This

  • makes modern digital cameras much more sensitive to the green part of the spectrum making pulling

  • a matte from greenscreen a little easier. Blue is still commonly used as are other colors

  • depending on the needs of the shot.

  • So now with advanced software and motion controlled cameras, Chroma Key, a term that has grown

  • now to encapsulate much more than it's original video technique, can be used to insert backgrounds

  • and set extensions in ways that Georges Milies and Norman Dawn could only dream of.

  • There are cynics today that believe modern film is too reliant on CGI and that we should

  • return to a simpler form of real filmmaking. But as I hope you learned, that era never

  • existed - filmmakers from the very beginning have sought to push the medium with special effects.

  • The undeniable truth about filmmaking is the only thing that matters is what's on that

  • screen. From Edwin S. Porter's matted train station window to the modern action spectacle,

  • it's all about creating a window onto another world. A world where each of us can find our

  • dreams our fears and ourselves. All these effects we have are just tools to help us

  • get there.. And we have some fantastic tools, so use them, and make something great.

  • I'm John Hess and I'll see you at FilmmakerIQ.com

[Class Assembling]

字幕與單字

單字即點即查 點擊單字可以查詢單字解釋

B1 中級 美國腔

好萊塢的假戲真做歷史|綠幕合成的發展歷程 (Hollywoods History of Faking It | The Evolution of Greenscreen Compositing)

  • 203 4
    AC 發佈於 2021 年 01 月 14 日
影片單字