I was thinking about using a Nikon D7100 with a capture card, since it has "clean output" HDMI (no menus or info ovelayed), but it has a 30 minutes maximum recording time according to https://www.atomos.com/cameras/nikon-d7100. Any ideas how to overcome that?

I've heard 30 minutes of video is the threshold for leaving the EU's 0% "IT Equipment" import tax category and entering the 5-12% "Video camera" tax category. https://www.tested.com/tech/photography/44445-why-digital-ca...

I found this tool that claims to be able to patch your firmware to remove the recording time limit, but I haven't tried it due to being a Sony guy : http://simeonpilgrim.com/nikon-patch/nikon-patch.html

dont't try - its going to burn the sensor, as it will overrun it's thermal capacity. this is why there is the 30 mins limit in the first place; you'll see a marked raise in noise after 10 mins or so any way

The limit is only for tax purposes. One guy at my work uses Sony DSLR as webcam and it works just fine and we are staying with cams/mics on for hours at a time (pair programming)

My D90 purchased in Europe kind of disagrees with you.

Indeed. My A7ii uses a very similar sensor to some Nikon cameras, and the sensor is literally always on, because the camera lacks an optical viewfinder. While the noise for very long exposures is negatively affected by the temperature of the sensor if left on too long without being allowed to cool down, the camera is made for having the sensor on for hours and hours every day without issue, and the Nikon sensors aren't any different.

Whats most likely to break, however, is the shutter mechanism. But even that isn't affected here.

I'm actually really upset that my Lumix LX100 doesn't support live hdmi output, I was hoping to use it as a webcam replacement but apparently Panasonic never implemented this feature, which is a shame because the picture quality would blow any webcam out of the water.

If you're on Linux and don't mind an unreliable hack where your video sometimes freezes, I was able to bodge the mobile app preview stream from my Lumix GX80 to appear as a v4l2 camera [1]

[1] https://www.mjt.me.uk/posts/wifi-streaming-video-lumix-gx80/

I thought the older ones weren't designed for it - they weren't designed to hold the shutter open, or use the sensor for long periods of time.

I assume that has changed.

Not sure that was ever the case. My Nikon from ten years ago had the 'bulb' exposure mode that would stay open until a remote trigger was released.

People have been doing hour long exposures with these cameras for years. Let alone Live View mode!

It's really moreso an excuse to up sell you on a video camera.