It seems as Lenovo finally noticed and fixed the low PWM frequency issue

[Puppy]

Many of Lenovo past models, especially the most expensive ones with higher resolution displays, used very low PWM frequency around 200 Hz in almost whole brightness levels range to control display backlight brightness. Such low frequency can cause eyestrain or headache. Recent NotebookCheck reviews reveals that Lenovo finally (?) noticed the issue and fixed it:

Lenovo ThinkPad T470s (Core i7, WQHD)
Screen flickering / PWM not detected

Lenovo ThinkPad 13 2017 (Core i7, Full-HD)
The display backlight flickers at 30860 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 90 % and below.

Lenovo ThinkPad X270 (Core i5, Full HD)
The display backlight flickers at 26040 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 50 % and below.

Lenovo ThinkPad T570 (Core i5, Full-HD)
The display backlight flickers at 26040 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 40 % and below.

[Puppy]

With an exception

Lenovo ThinkPad T470s (7300U, FHD)

The display backlight flickers at 219.3 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 99 % and below.

[Thinkpad4by3]

Lenovo solution on the T480 will be little shaded glass slides infront of the led backlight that will be embedded in the lcd to control the level of brightness. Take apart the entire lcd to go from 50% to 40% - David "make your eyes Hz from flicker" hill. Lol. Also, only 10% birghtness will come in the box. Each sold seperately at 40$ each.

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