Broadcast cameras (Blackmagic Pocket Cinema Camera) or CCTV cameras won’t do this. An overlay is more of an issue with consumer camcorders and DSLRs, since the output is intended for preview and not recording.
Many DSLRs (like the Canon t3i we have here at LZX) can work on alternate firmware that enables more options for disabling the overlay text.
If you can specify model numbers on your camera we can see what’s possible! A recommended cameras thread would be great.
Admin notes: Edited subject for clarity and moved this to Pro Video & Broadcast
In the past I’ve found that if using older cassette based camcorders replacing the internal battery or simply loading a cassette in the camera will sometimes disable any onscreen icons in the live output feed.
Yeah this has happened with several cameras to me, you need to find the OSD (on-screen-displpay) and set it to OFF/Disabled so you dont have any visual feedback/outputs in your screen or video outputs.