Blackmagicdesign ATEM Live Installation And Operation Manual page 141

The chroma sample setting lets you position a cursor over the screen area you want to sample
TIP You can also view the M/E 1 preview output on your switcher's front
control panel LCD by pressing one of the auxiliary output buttons, then
pressing the ME 1 PVW button.
4 Click and drag on the box cursor to move it to the position you want to sample.
To set up a chroma key on upstream keyer 1 on an ATEM Advanced Panel:
1 Press the 'key 1' button to enable keyer 1 on the preview output. This automatically
selects the keyers menu on the system control LCD, but you can also press the 'keyers'
button to enter the menu directly.
2 Select the 'chroma' key type using the corresponding 'key type' control knob.
3 Select your fill source by turning the corresponding LCD control knob. Typically, this
source would be from a camera facing a presenter in front of a green screen, or a
graphic loaded in a media player. You can also select a fill source by pressing the
corresponding button in the source select bus.
4 Use the 'right' arrow buttons to access the chroma adjustments screen.
5 Click the 'sample chroma' button.
Choose a representative area of your green screen that covers as much of the luminance range
of the screen as possible. The default size of the box cursor is well suited to most green
screens that are relatively evenly lit, however if there is a lot of variance in your green screen,
you can adjust the size of the box by clicking on the slider to the right of the sample window
and dragging it up or down. On ATEM advanced panel, use the joystick to move the position of
the box and the z axis to increase or decrease the size.
TIP When sampling uneven green screens, we recommend sampling the darkest
area first before increasing the size of the sample box. This can give you a more
accurate key.
You can preview your key at any time by clicking the 'preview' button above the chroma sample
panel or by pressing the 'preview chroma' button above the LCD screen on the
advanced panel.
Keying using ATEM Switchers 141