Подсветка вспышки - красная точка (на самом деле, инфракрасная), которую легко детектирует фазовая система зеркалок, AF зеток понимает только зеленую или синюю. Вспышки для зеток должны перейти тоже на зеленую.
Мансуров:
Like other mirrorless cameras, the Nikon Z9 cannot trigger the autofocus assist lamp of most flash units. Nor would it do much good if it could, because those flash units emit red/infrared light that is easy for a DSLR’s phase detect system to pick up, but not very useful for most mirrorless AF systems. If the problem is to be solved, flash companies will need to release a flash with green or blue light AF assist lamps in the future. (Or, flash photographers will need to live with other, less obtrusive focusing methods in low light.)
https://photographylife.com/reviews/nikon-z9
