There are two types of capturing evidence of them on high end 4k video. One is by filming through the medium of reflections in black mirrors or any possible reflection where you might suspect them to be. The second method is by using a higher end camera phone like the Samsung Galaxy s21 ultra and adjusting the camera settings to disable steadyshot or keep it on. Also auto frame rate is best rather than choosing 30 60 or 120fps. The video below is reflection of my office desk through a metallic mirror. The key moment occurs at 6:15 in the center of the frame. Also note that if you open the file with QuickTime player and use frame by frame control left to right the subjects alternate in color strobing between green and light red.

https://drive.google.com/file/d/1OfyHQiBnOfB65MBaoqI6bm9uYQfvr-gR/view?usp=drivesdk

Download for full res file.

6:15

The second method is to direct your camera (I'm my case the galaxy s21 ultra set at auto full res auto fps) and when you scan the room you suspect the entity to be in, you will notice the camera image jumping abnormally and jumpy bc it detects something but can't quite capture it. You will also sometimes notice significant distortion in the image that should otherwise be very clear and sharp.

Example of detection via scanning room:

https://drive.google.com/file/d/1OOwa-s9rDpsICFVi--ED0DJqxsvan7u4/view?usp=drivesdk

Example of distortion:

https://drive.google.com/file/d/1WwrJJJESbX26t5zlCVhf9h3nle_MnRPf/view?usp=drivesdk