Screen Capture source can be used to monitor the images / videos directly from the screen.
It can be used to monitor photo-editing apps like Photoshop, Lightroom or Capture One. It can also be used to monitor video sources like YouTube or Vimeo videos directly.
Once the Screen Capture is connected you can specify the source screen in the settings:
In the new dialog box you can select the monitor that will be used as a source:
You can also limit the frame rate of the capture process.
Then to adjust the captured source you can use the Crop feature – View menu / Crop or Alt+C keyboard shortcut:
This way you can limit the captured area to the monitored image only.