You’re right - looking at the scope pictures, the horizontal period of the grid is 2ms, and the period of the wave is just over that.
A 240Hz wave would have a period of 4.17ms. 480Hz is 2.08ms. Much closer to the oscilloscope waveforms. And even then the waveforms are periodic, with smaller troughs at every second dip.
I wish I could see their test setup. It would be ironic if the panel was fully DC dimmed and the troughs were from another light source or something…
I’m not sure why the scope is saying 240 though. It makes me doubt my understanding :-/.
[Edit: Ah - got it! It’s measuring the frequency of the very lowest points - the ‘every second dip’]
The difficulty here is that it's 480Hz top-to-top, but there are two definitions of dip-to-dip depending on if you count every 'dip' from 100% (480Hz), or just the ones that reach the lowest voltage ⃰ (240Hz).
⃰ ⃰(brightness - presumably the test setup is an LDR or something?)
Here's my hypothesis: I'm guessing that the reviewer is using some kind of photodetector that is sensitive, to different extents, to different portions of the screen. And that the actual display modulates at 240Hz but that some portions of the screen are 180 degrees out of phase with other portions. Or that one of the subpixel colors is out of phase with the others. This could explain the weird alternating-depth signal at ~2ms intervals.
That doesn't look like it's even close to being able to focus on a single subpixel or even a single row without additional optics.
In any case, the 0% and 25% waveforms look pretty bad. In my experience, light with sharp, short pulses (like "driverless" LED lights produce) are unpleasant, but the unpleasantness is related to how bright the source is compared to everything else in the field of view. (The 0% and 25% waveforms are solidly at twice the frequency of driverless LEDs, which will make the effect considerably less bad.)
A 240Hz wave would have a period of 4.17ms. 480Hz is 2.08ms. Much closer to the oscilloscope waveforms. And even then the waveforms are periodic, with smaller troughs at every second dip.
I wish I could see their test setup. It would be ironic if the panel was fully DC dimmed and the troughs were from another light source or something…
I’m not sure why the scope is saying 240 though. It makes me doubt my understanding :-/.
[Edit: Ah - got it! It’s measuring the frequency of the very lowest points - the ‘every second dip’]
⃰ ⃰(brightness - presumably the test setup is an LDR or something?)
Here's notebookcheck's review methodology:
https://www.notebookcheck.net/How-does-Notebookcheck-test-la...
And the sensor they use might be this one:
https://www.thorlabs.com/item/PDA100A2
That doesn't look like it's even close to being able to focus on a single subpixel or even a single row without additional optics.
In any case, the 0% and 25% waveforms look pretty bad. In my experience, light with sharp, short pulses (like "driverless" LED lights produce) are unpleasant, but the unpleasantness is related to how bright the source is compared to everything else in the field of view. (The 0% and 25% waveforms are solidly at twice the frequency of driverless LEDs, which will make the effect considerably less bad.)
Surely someone on HN has the equipment and curiosity to double-check all this as a Sunday afternoon project?…