3
Use the control knobs under the LCD menu to select the fill source and key source. You
can also use the corresponding source select buttons to select the fill and key source.
4
Once you have chosen the fill source and key source, use the ‘left’ and ‘right’ control
buttons to scroll through additional menu screens containing key parameters such as
mask, gain, clip, pre multiplied key settings and more.
Chroma Key
Chroma key is commonly used for weather broadcasts, where the meteorologist appears to be
standing in front of a large map. In the studio the presenter is actually standing in front of a blue
or green background. In a chroma key two images are combined using a special technique and
a color from one image is removed, revealing another image behind it. This technique is also
referred to as color keying, color-separation overlay, green screen, or blue screen.
A very common use for chroma keys for backgrounds is computer generated graphics. It’s
simple to connect an external computer to your ATEM switcher using the HDMI output of the
computer or a video card such as the Blackmagic Design DeckLink or Intensity range and then
play back video clips to your ATEM switcher. If you render a green background on your
animations, you can then key this green to create fast and clean animations of any length.
Keying is easy as the green is computer generated so it’s a very flat color that’s easy to key.
Combining a background with a fill and chroma key/cut
Background
A full screen image; in the case of a chroma key it is often a weather map.
Fill
The image you plan to display on top of your background video. In the case of a chroma key,
this is video of the meteorologist in front of the green screen.
Key/Cut
In the case of a chroma key the key/cut signal is generated from the fill signal.
Performing an Upstream Chroma Key
Use the following steps to perform a chroma key on ATEM Switchers. ATEM 4 M/E Broadcast
Studio 4K has its own unique chroma keyer with advanced controls. For more information, refer
to ‘Performing an Advanced Chroma Key’ later in this section.
To set up a chroma key on upstream keyer 1 on the software control panel:
1
Expand the upstream key 1 M/E 1 palette and select chroma from the key types bar.
2
Select the fill source.
3
Adjust the key parameters to refine the key. For a description of chroma key
parameters, refer to the table below.
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Keying using ATEM Switchers