When I shoot pictures of badgers I recently found that the Nikon D500 + 200mm F/2.0 is a great combination. Badgers often come out very late when its quite dark but they cant see too well so you can get relatively close to their den. I used to shoot the 200-400mm F/4.0 but the 200mm F/2.0 gives me two stops more light which gives me almost an hour of extra time when the sun sets.
The only problem is: Focusing can get tough sometimes.
My question is: Could an infrared torch be used to assist the focusing of the camera? I guess that it wont work with mirrorless cameras like the Z7 (or in live view with the D500) since they should have an infrared filter and the focusing gets done at the sensor plane but the D500 has a dedicated autofocus sensor bay.