Lenovo T500: measuring screen flickering

Lenovo T500 was one of the first laptops with LED backlight. I've used also R500 with CCFL and I would actually prefer it over T500. R500 had more natural colors (no bluish hard to correct hint like with T500) and I hadn't noticed any screen flickering. With T500 flickering is quite noticeable when e.g. moving fingers before the screen.
How bad is it?
To measure actual flickering frequency I've connected small photovoltaic battery from old calculator to USB oscilloscope input (1M input impedance) and put 100k load resistor in addition.

T500 has 16 brightness levels, here are some captured waveforms from photo cell in front of the screen:
lowest brighness (aka level01): 100Hz pulse period

level02: similar amplitude captured (pulse width) but 220Hz pulse frequency

level05: higher amplitude (probably wider pulse), same frequency

level 10


level14: roughly 50% pulse width

level15: pulse width over ~66%, same frequency (still 220Hz)

level16 (brightest): no flickering

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