TechSensitive Thank you again for the reply. I am really grateful that you are sharing all this knowledge here.
I can make a video with my camera of the devices and post it here.
Basically my issue is very simple -
on my old Acer laptop (5820tg) with win 7, I have no issues on all brightness settings
-my iphone 4s also gives me no issues on all brightness settings
-i use external display, ASUS pb238q, which on 100% brightness gives no issues, on less it starts to bother me. It has confirmed PWM so I guess that is the reason.
-my Nikon d800 camera display causes me similar symptoms, but luckily I dont have to look into it all the time
Anything else Ive tried recently from new tech (some macbook 13in, 15in, iphones 6, 6s, 7, Dell xps 15 2017 - one was ok, but i returned it as it was bad config, another one caused the issue), causes me instant discomfort and headaches progressing to migraines, similar as to when I decrease the brightness on my ASUS external screen.
The difference is immediate, so I do not believe other lighting in the room, my distance from the device etc. would play a role here. Simply, put an iphone 7 next to my iphone 4s on a table, one will be ok, the other will cause almost instant pain and discomfort.
That is why I wanna measure these devices with all possible tech I can think of, to see whether there really is some difference, and what it is.
I am taking MacuShield supplements to rule out blue-light sensitivity, but its gonna take proper effect in a month or bit more.
The thing with the microphone sounds interesting, I will research it, however from your descripton it seems more complicated than learning how to use an oscilloscope. Also wont probably work with the phone and other displays. Ill see about both options.