Forma Couldn't detect screen flickering on Kobo Forma. Does it mean no PWM?

[rbyl]

I understand that there are a couple of threads already opened in forum discussing about screen flickering on Kobo Forma.

The purpose of this thread is to share how I tested my unit and hopefully someone can enlighten me if there is any better way to test (not requiring scientifically high-precision-advanced tool).
Also I'm curious how other forma users test their unit (if there is any testing done ) and what is the result?

I tested using Iphone 7 Plus recording slow-mo video @ 240 fps.
Testing was done in a room with various lighting condition i.e. very dark, dim, well-lit with artificial light, and well-lit with natutal light.
Also, the screen was tested on different light intensity from lowest to highest and in-between. Also the kobo was set to both potrait and landscape orientation.

As a result, I couldn't see any flickering at all. Does it mean there is no PWM?

Part of me says I could be one of those fortunate to get non-defective unit.
Like Kobo Clara HD model, while many users reported light-bleeding issue, my unit is does not suffer from this and I'm very much enjoying it.

[DNSB]

Originally Posted by rbyl

As a result, I couldn't see any flickering at all. Does it mean there is no PWM?

Part of me says I could be one of those fortunate to get non-defective unit.

If Kobo is using PWM which is very likely since it does have several advantages, the question becomes what is the frequency at which the PWM operates. The last device (not an ereader) I played with used a 2KHz frequency for it's PWM which is fast enough that I don't think anyone will be noticing it.

[ReaLx3m]

240 fps videos on youtube show 3-4 lines(more like 4), so i think it would be safe to asume its at 720-960hz