Lesson 11 (Five Class Periods)
Chroma Key – Troubleshooting and Effective Use
In this lesson, students will learn to use keying effectively, and apply chroma key to the live broadcast journalism component with weather forecasts. Although there are many uses for chroma keying, news rooms tend to use keying mostly when reporting the weather. Students will also learn what works and what doesn’t work when using the chroma key feature (frizzy hair, for example, does not work well with keying).
Things that don’t work
Clothing that’s the same color as the chroma mat/chroma wall
Additionally, students will understand the process of producing a live weather segment for their broadcast. Students will divide into groups and produce a weather segment, assigning each group member different tasks (script writing, meteorologist, camera operators, technical director) and perform the segment live in front of the class.
Good Chroma Key Techniques:
The recipe for a perfect key is to point the cameras directly at the chroma wall/screen and a wave form monitor. Set the lighting so that the wave form register is at 50%. The goal is to achieve even light (one of the biggest mistakes people do when keying is to overlight the set). Have students stand at least four feet in front of the chroma wall/screen and light them as you normally would with three-point lighting (See Lesson 4). To avoid drop shadows (casting shadows on the chroma wall/screen), it’s imperative students stand at least four feet from the wall/screen. Once students are in front of the wall/screen, adjust the tolerance to where the student’s body is solid (not transparent). By adjusting the tolerance, you can achieve a cleaner key.
An understanding of chroma key and how this feature works
Using chroma key in a live broadcast situation (reporting weather)
What works and what doesn’t work when keying
Converting web images into JPEGS or PowerPoint slides
Activity 1 (Day 1): In groups of five or more (if the class is small, two groups will be sufficient), students will visit the noaa (National Oceanic and Atmospheric Association) website and download weather pertaining to their assigned area (the teacher can assign a specific area for each group or each student group can choose their area). Students will convert the weather into PowerPoint slides. Be sure that the students gather forecast information and satellite information. (These web images can be simply copy and pasted into PowerPoint, or saved as a JPEG file and then placed in the PowerPoint)
Activity 2 (Day 2): Students will take the information they gathered during Activity 1 and input the information to a graphic. Students can begin to experiment with lower-thirds. For example, a student can write the name of the weather person in one of pre-made lower-third features.
Activity 3 (Day 2 and 3): Students will begin experimenting in front of the chroma screen (this can be achieved through chroma paint, chroma mat or chroma fabric/paper. Below are links with more information on chroma wall solutions:
At this time, students can experiment with what works and what doesn’t. For example, someone with big or frizzy hair, or a student with the same color of clothes as the chroma wall/mat would not create a good key. (Refer to the above introduction pointers for keying instructions and pointers)
After experimenting with keying, have student groups begin to write a one-minute weather script. Student groups will designate a director, weather person, camera operators (depending on the number of cameras available), and a technical director (someone to switch the cameras). PLEASE REFER TO LESSON 8 Show an example of a news weather cast and have student groups model their scripts after the weather segment. It’s up to the teacher whether or not freedom of creativity is given to the students (for example, a silly weather report or a serious weather report).
Activity 4 (Day 4 and 5): Student groups will present their weather report live to the class. Students will be expected to use lower thirds and transitions integrate the PowerPoint slides or JPEG images copied from NOAA.gov, as well as switch cameras.
Handout (To be created)
One to three cameras (preferably more than one for switching purposes)
An area or wall for chroma key
Microsoft PowerPoint program
Anticipatory Set (Day 1):
Show a local news weather segment and ask the class if anyone knows how the information is displayed behind the weather person. Explain to students the function of keying and what it’s used for. Below is a link with more information:
Students will learn how to properly key as well as understand the function of chroma key. Students will also obtain an understanding of how to produce a basic weather segment.
Input (Day 2 and 3)
As a class, students will begin to experiment with keying. Students will take turns on the video switcher/mixer while other students and/or the teacher provide examples of what works and what doesn’t work against the chroma wall/screen. Examples should include:
What doesn’t work:
Clothing similar in color as the chroma wall/screen
What does work:
Contrasting clothing against the chroma wall/screen
Explain to students how to achieve good keying.
Good Chroma Key Techniques:
The recipe for a perfect key is to point the cameras directly at the chroma wall/screen and use a wave form monitor. Set the lighting so that the wave form register is at 50%. The goal is to achieve even light (one of the biggest mistakes people do when keying is to overlight the set). Have students stand at least four feet in front of the chroma wall/screen and light them as you normally would with three-point lighting (See Lesson 4). To avoid drop shadows (casting shadows on the chroma wall/screen), it’s imperative students stand at least four feet from the wall/screen. Once students are in front of the wall/screen, adjust the tolerance to where the student’s body is solid (not transparent). By adjusting the tolerance, you can achieve a cleaner key.
Model (Day 1 and 2)
The teacher will provide examples during all activities (showing students how to obtain the weather graphics, how to convert them to PowerPoint or JPEG and how to input these, as well as show students how to operatea chroma key function.
Check for Understanding (ongoing)
Since students will be taking a “hands-on” approach, the teacher will be able to assess if students are understanding and retaining the lesson.
Guided Practice (ongoing)
Students in their groups will work together with the teacher to obtain weather information, write the weather script and work with keying, lower-thirds and transition functions.
Closure (Day 4 and 5)
Student groups will present their weather reports live to the class. Student groups will demonstrate their knowledge by presenting the weather report in a timely fashion (no more than one to two minutes) and use of a video switcher/mixer (switching, lower-thirds and transition abilities). Students will also demonstrate their ability to work together as a team.
Through a mentorship program (arranged in prior lessons), or through contacting a local weather person, arrange for the weather person to come to the school (or students going to the station) and discuss with students what goes into producing the weather broadcast, how the meteorologist works with the news crew, what types of credentials are needed to become a meteorologist and the salary.
Integration into live broadcast
Integrating a weather segment into your live broadcast ensures students will continue to use and understand the chroma key feature, as well as understand how weather information is acquired and how to use this information in a live broadcast.
National Educational Standards Met
Language Arts, Standard 1: Read a wide range of print and non-print texts to build an understanding of texts, of themselves and of the cultures of the United States and the world; to acquire new information, to respond to the needs and demands of society and the workplace, and for personal fulfillment.
Language Arts, Standard 4: Adjust their use of spoken, written and visual language to communicate effectively with a variety of audiences and for different purposes.
Language Arts, Standard 7: Conducts research on issues and interests by generating ideas and questions, and by posing problems. Gather, evaluate and synthesize data from a variety of sources to communicate discoveries in ways that suit purpose and audience.
Language Arts, Standard 8: Use a variety of technological and information resources to gather and synthesize information and to create and communicate knowledge.
Civics, Standard 5: Citizen responsibilities, citizen rights
Technology, Standard 4: Students use telecommunications to collaborate, publish, and interact with peers, experts, and other audiences.
Technology, Standard 5: Uses technology to locate, evaluate and collect information from a variety of sources.
Technology, Standard 6: Uses technology resources for solving problems and making informed decisions; employs technology in the development of strategies for solving problems in the real world.