Lattitude 5520 PWM flickering

Question

Hi all! I bought Lattitude 5520-0501 for my mom. I noted that it seems has PWM flickering. I tested it with pen-test and also with slow-motion video, record may be seen here https://www.youtube.com/watch?v=JypUz7t1uEs Also I checked it with AIDA64 and it tells it has IPS panel VNCT2_156DL02 (NCP0057). Also 5520-0501 model info states it has Dell panel part number 391-BFPM. There is not so much information on internet about that panel, only 1 site and it notes it has flickering at 1050Hz. (https://laptopmedia.com/screen/vnct2-156dl02-ncp0057/) As for now, for the stated reason, I'm going to return this laptop to the store. And now I consider model 5520-0532 or 5520-3473. They are equipped with another panel, part number 391-BFPQ, 1920x1080, WVA, SLP, ComfortView Plus, 400 nit. I ask, maybe someone knows, does the panel used in 5520-0532 or 5520-3473 have no PWM flickering? This knowledge will save my time a lot (if it also has PWM flickering, I just will skip the model at all). Thank you!

Radiochemist · Answer

I came across this review awhile back when deciding which model to choose and remember that at least one display panel the unit ships with (and things change, but usually not with regard to PWM due to the differences it creates some headaches (literally and technologically) and so if a model says it doesn't have it, I tend to believe it.  What do you think of this?  Might it help?  They state at the site linked: PWM (Screen flickering) Pulse-width modulation (PWM) is an easy way to control monitor brightness. When you lower the brightness, the light intensity of the backlight is not lowered, but instead turned off and on by the electronics with a frequency indistinguishable to the human eye. In these light impulses, the light/no-light time ratio varies, while brightness remains unchanged, which is harmful to your eyes. You can read more about that in our dedicated article on PWM. Dell Latitude 15 5520’s display doesn’t use PWM to adjust its brightness levels at any point. This makes it comfortable for long work periods, without harming your eyes in this aspect.https://laptopmedia.com/review/dell-latitude-15-5520-review-paving-the-way-to-sustainability/

pavelvasev · Answer

Dear Radiochemist, thank you for your reply! I read those article on laptopmedia.com and I read their note about PWM. And I used exactly that article as a decision making information when to purchase that laptop, exactly Latitude 15 5520-0501 model. And when it came to me, I was absolutely sure that it has no PWM (because those respected article claimed this). Until I decided 'just for fun' to perform a pen-test and noted that results looks like not the same as on my 'certified flicker-free' Dell monitor. Then I recorded slow-motion video and posted it on youtube, and returned laptop to seller (thanks they grace a 1-week period to return without any reasons). Probably, I am not right, because I'm not expert in such a manual PWM determination. But.. I can't risk, because the laptop is for my mom. By the way, what do you think of the video, is it PWM or not? // https://www.youtube.com/watch?v=JypUz7t1uEs

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