...set smaller canvas in OBS Settings > Video
OBS "Settings" can be opened from the "Controls" panel (the button "Settings" below "Studio Mode" button) or from the main menu "File".
There is too options in the "Video" section of the "Settings":
- "Base (Canvas) Resolution" in format Width by Height, in pixels;
- "Output (Scaled) Resolution" in format Width by Height, in pixels.
Canvas - is place where all the graphic sources lie. A smaller sources can be placed side by side if the canvas is large enough. Some large sources can lie beneath smaller sources (like picture-in-picture) and so on.
Output - is final size that saved in a file/stream, it usually should match the Base (Canvas). Sometimes, users need a larger canvas (full-screen 4K display) that is scaled down at the output (for example, for 720p HD streaming with lower bandwidth requirements over a busy network). Here, lower resolution = lower network bandwidth requirements.
If you remember, OBS is a tool for streamers and gamers, so there are so many options. To learn more about OBS:
OBS (Open Broadcaster Software) is free and open source software for video recording and live streaming. Stream to Twitch, YouTube and many other providers or record your own videos with high quality H264 / AAC encoding.
obsproject.com
and
Guides for OBS Studio
obsproject.com