Article by Alice Shown
Since technology has finally caught up to the business worlds need for quick and effective web videos, special affects like Green Screen are now available to just about everybody who is doing business videos. Heres how to shoot great footage for your green screen affect.
WHAT IS GREEN SCREEN AND HOW DOES IT WORK?Green Screen (also called Blue Screen and Chroma Key) got its start in the 1930s when a movie maker at RKO Studios named Linwood Dunn wanted to create exotic imagery never before seen in movies in The Thief of Bagdad (RKO 1940). TV weather men started interacting with their weather maps in the 1970s using early digital technology of the chroma key format. Digital chroma keying is what makes green screen technology possible today.
Where movie makers had to arrive at this affect through painstaking methods involving multiple shoots of the same scene and extracting imagery through subtractive and additive lens filtering and frame by frame moving mask editing, todays videographers can simply shoot their talent in front of a solid colored screen in order to replace that color with preselected footage. Weather meteorologists on The Weather Channel as well as network and local TV stations use the same technology to interact with a weather map. (It is noted that some meteorologists also use a new giant plasma or LCD TV screen to arrive at the same affect. This giant screen is real and the meteorologists are actually standing in front of it.)
The Chroma Key Affect is a product of three elements; Lighting, Stage Blocking and Post Production Software. To make it work, computerized digital editing software senses the solid color and replaces it with selected footage. The talent is located in front of the replaced footage as part of the shot. Since the affect is a combination of good lighting and computer processing, green is the most common color used for most applications because of its furthest tonal proximity from flesh tone. Blue is also used for some applications for the same tonal reasons. Green works best under most conditions for color purposes. Yes, green and blue clothes will also key out in front of these screens so apparel planning is important. Basically, you are trying to create an environment in front of the camera where the person is generally any color but green, and the screen is only green. Therefore, the software will see two conditions;green and not green.
ITS ALL ABOUT LIGHTINGIn order to allow the video camera and therefore the computer to see both the talent in front of the screen and the screen clearly, adequate lighting is necessary of both. It is best to light the screen first from left and right using very dispersed, unfocussed lights, then light the subject, and then go back and adjust the screen lights again as needed. But, the true test is with the software which is to be used for the affect. Having a test run or live run of the affect is important before committing assets that may not be available at a later date. Rolling footage is better than live camera signal for the test as it best represents the elements with which the software will be working.
The goal in lighting the screen is to wash it in warm, even lighting. More light is not necessarily always better. A lot of the success of the process depends on the professional level of both the camera and the technicians in post production. The trick is to find that perfect lighting contrast difference between the talent and the screen which the software finds most accommodating. All software sets and cameras are different. But this is really a lot simpler than it sounds when described technically in an article such as this because the computer does all the heavy lifting. But, if you have lit your subjects well (the screen and the talent), youll have no problem.
THE SETIt is important that shadows from the talent do not wash across the screen. Therefore, place the talent far enough in front of the screen that the lighting from the talent does not effect the screen. The talent needs to keep all body parts in front of the screen from the cameras point of view. Any arm and hand flinging further than the boundaries of the screen will end up looking like the talents arm or hand suddenly was surgically cut off and then replaced again.
To create the set for a green screen, one simple way, weather permitting is to shoot outdoors in front of a green wall in full sunlight. (This works great. I did it myself for a 1986 production for the Chicago Arch Diocese titled Saints Are People Too 1986 Video Images, Inc. We set up a blue screen suspended on all sides by a portable frame in front of which children ran and jumped. Separate computer processed technology was used to reveal rainbows trailing each child in a psychedelic music video scene.)There are portable, good-to-go screen sets that can be found online like ChromaPop. Or, do-it-yourselfers can simply suspend a thick green cloth and light it really well. Once again, make sure to run a test strip of footage through your computer software to make sure the screen is adequately lit.
Common application of the Green Screen in business and commerce videos is the talking head. It is much more interesting to present important information in front of a digitally produced background than a curtain and a potted plant. Check out this well crafted example at EZWebPlayer.com. The short video shows the president of the company with various animations going on as his background.
WHAT NOT TO WEARIf you are shooting in front of a green screen, avoid wearing green clothes. Even a persons green eyes can be accidently keyed out, especially on close ups and medium close ups. If this is a problem, adjust lighting to make the green screen as bright as possible, or switch to a blue screen. If the screen is a bright green and the suite is a very dark but well lit green, the process might work. Test, test, test.
DID I MENTION RUNNING A TEST?Since lighting is everything, and lighting is not necessarily a straight forward process to the un-initiated, testing becomes all important. Our company shoots green screens regularly (more than once a year) in our own studio and we still run tests through the software before shooting the script. Testing will show inadequate lighting areas on both the screen and the talent in front of the screen.
After capturing your chromakey footage, you simply treat it like any other footage to import into your editing suite. In the category of green screen, you are now well on your way to getting video on your web site.
Stu Marks is a veteran video producer specializing in business and commerce videos for the web. His experience dates back to the early days of video in its two-inch and one-inch formats of the 1970s as he was shooting local commercials and political forum videos, and carries him all the way through a bachelors degree from The Illinois Institute of Art at Schaumburg / Chicago Art Institute in MultiMedia and Web Design in 2004. Today, Stu is the Art Director at IncreaseSalesWithVideo.comin Chicago.
LinksEZWebPlayer. The no-tech solution to placing videos on your web site.http://www.ezwebplayer.com
ChromaPop. Portable Green & Blue Screenhttp://www.digitaljuice.com/djtv/detail.asp?sid=435&sortby=&page=1&rpid=0&rvid=0&swid=0&searchid=0&gclid=CJ-1uYW3qKUCFQNrKgodTEfiGw
September 25, 2011
Green Tech