During the COVID-19 Shelter-in-Place we’ve been on video conferences a lot more than usual. To use your Sony Camera or Canon DSLR as a webcam without a capture card here are some things you can do.
I have successfully tried this with a Sony RX100 VA and a Sony A7ii and a Canon SL1 though not every model works.  You will need CamTwist for either camera and additional software for Sony and Canon.

Install CamTwist for both Sony and Canon.

1. Install CamTwist
1. http://camtwiststudio.com/download/
2. Start CamTwist
3. Open Preferences
4. Set your video size, I use Custom and 1920×1080
5. Set your Frame rate, I use 30. 
6. You will have to restart CamTwist for the changes to go into effect.

Sony (kind of a hack)

Sony cameras must support Display Live View which can be seen here https://support.d-imaging.sony.co.jp/app/imagingedge/en/devices.

1. Install Sony Imaging Edge Desktop.
1. https://imagingedge.sony.net/en-us/ie-desktop.html
2. Install Sony Remote from the Imaging Edge application.
3. With your camera set the USB Connection to PC Remote
1. For the RX100 VA (new sony menu) it was under Setup3
2. For the a7ii (original sony menu) it was under ……
4. Turn on your camera
5. Plug in a micro usb cable to your camera and the computer.
6. Start Imaging Edge Desktop
7. Click Start for Remote
8. Double Click on your Camera with the pop up.
   
9. The Remote Application should show up with a live preview.
10. Start CamTwist
11. Select Desktop+, then click Select
12. Under Settings unselect Full Screen and select Confine to Application Window.
13. From the Select from existing windows select Remote (Remote)
14. Select Resizeable selection.
15. Click Select capture area. 
16. Position the rectangle over the live preview.
17. When you start your video conference software, like zoom, go to Prefences->Settings->Video->Camera and select CamTwist.

Note that you must leave the Remote application running and up on the screen but you can obstruct it and put other windows on top of it and still use it as a webcam.

Canon

For a list of supported Canon Cameras go here: https://github.com/v002/v002-Camera-Live/blob/master/CAMERAS.md

1. Install Camera Live, I’ve linked a stable release as of today.
1. https://github.com/v002/v002-Camera-Live/releases/download/11/Camera.Live.zip
2. Their github (for coders)
2. Turn on your Canon DSLR.
3. Connect your usb cable to the Canon and the computer.
4. Start Camera Live
1. You should see Active for your camera in Camera Live.
5. Start CamTwist
6. Select Syphon
7. Click Select
8. In the Settings section under Syphon Server select Camera Live.
9. When you start your video conference software, like zoom, go to Prefences->Settings->Video->Camera and select CamTwist.