Your interior camera works fine in the daytime. That is the problem, because daytime is not what you bought it for.
Most incidents involving a passenger happen after dark. That is when the fare gets strange, when the disagreement starts, and when you most want a record of who said what. It is also exactly when a lot of interior cameras stop being useful, because the inside of a car at night is genuinely dark. There is no streetlight in your back seat.
If your camera depends on visible light, it has almost none to work with. You end up with footage showing a shape moving in a seat. You can tell somebody was there. You cannot tell who.
A recording that proves a person existed is not evidence. It is a shape.
What infrared actually does
Infrared closes that gap. Instead of relying on whatever light happens to be in the car, an infrared camera provides its own, at a wavelength your eyes cannot see. The camera gets a lit scene. Your passenger gets a dark car, because from where they are sitting, nothing has changed.
Wavelength is the first thing to check. Some cameras use 850nm, which works, but the emitters glow a faint red that people notice in a dark cabin. A camera that visibly lights up invites a conversation you did not want to have at one in the morning. The Nexar cameras you can buy for your own car all use 940nm instead, which sits far enough outside human vision that nobody sees anything at all.
The second question, about daylight
There is a second question, and it is the one that rarely makes a spec sheet. Infrared does not switch itself off when the sun comes up. On a lot of interior cameras, that leaves a purple cast across daytime footage, and it is exactly the sort of thing that makes a clip look unreliable when somebody else is watching it.
Beam4 handles this with an RGB-IR sensor, which separates the infrared from the visible light rather than letting them mix. You get infrared at night and clean colour in the day, from the same lens, with nothing to switch.
So when you compare interior cameras, ask about both. Not just whether it can see in the dark, but what it does to your footage in bright light.
What to look for when you compare
Resolution matters less here than you would think. A 4K interior camera with no infrared still gives you a dark rectangle at night. A 1080p one with infrared gives you a face.
Beam4 records the cabin at 1080p and 30fps across 132 degrees, at F1.7. The aperture is the quiet part of that. A faster lens takes in more light before the infrared has to do any work, which is why it matters more on an interior camera than the pixel count does.
We put the 4K on the road-facing lens, where reading a plate at a distance is the job, and built the interior lens around seeing in the dark instead. For a camera pointed at your back seat, that is the trade worth making.
Both lenses sit in one unit and move together, so aiming is one job rather than two. The cabin lens has a 20 degree tilt built into it, which means once your road view is level, your interior is already covered.
Beam4 also records three audio channels, picking up sound from inside the car and outside it. Audio is often the part that settles a dispute, though the rules on recording it vary by state, and that is worth reading up on before you rely on it.
Telling your passengers
Most rideshare platforms allow interior cameras, but disclosure requirements differ depending on where you drive, and a sticker on the window is cheap insurance. Infrared changes what your camera can see in the dark. It does not change what you are obliged to tell people.
Three things to check
If you drive at night, check three things on any interior camera before you buy.
Does it have infrared, and at what wavelength? What happens to your daytime footage? And can you see a recognisable face in a real clip, rather than a demo reel shot in a lit studio?
That last one is the test that matters, and it is the one nobody publishes.