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Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 27,305
Message 1 of 49

Low PWM frequency affects recent ThinkPad models

Lenovo,

 

you know that there are customers who complains about poor quality of displays in high-end premium price ThinkPads. Recent reviews reveals another serious issue, low PWM frequency ~220 Hz is used to control display backlight brightness in almost whole brightness setting range. Such low PWM frequency can cause eyestrain. Competition does not have the issue so aggresive, their displays does not use such low frequency or it affects smaller brighthess settings range like 0% to 20% only.

 

Since the issue affects multiple recent ThinkPad models it might indicate some improper BIOS / drivers code that controls the display.

 

Lenovo ThinkPad T460s (Core i7, WQHD)

http://www.notebookcheck.net/Lenovo-ThinkPad-T460s-Core-i7-WQHD-Ultrabook-Review.161028.0.html

 

The display backlight flickers at 220 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 90 % and below

 

Lenovo ThinkPad X260 (Core i5, WXGA)

http://www.notebookcheck.net/Lenovo-ThinkPad-X260-Core-i5-WXGA-Notebook-Review.161003.0.html

 

The display backlight flickers at 220 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 90 % and below

 

Lenovo ThinkPad P70 Workstation Review (4K)

http://www.notebookcheck.net/Lenovo-ThinkPad-P70-Workstation-Review.158308.0.html

 

The display backlight flickers at 228 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 95 % and below.

 

According other reviews (P50, E560, T460p), 15.6" FHD IPS displays (LP156WF6) and some 14" FHD IPS displays (LP140WF6) are not affected by the issue. Both made by LG.Display, any clue ? Is possible to fix that by BIOS or customized video drivers update ? Thanks.

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 27,082
Message 2 of 49

Re: Low PWM frequency affects recent ThinkPad models

I selected some other reviewed models to show there must be something wrong with Lenovo display brightness PWM control in general because no other vendor have such issues. Please do not delete the post just because it compares Lenovo models to the competition, it is the only way to demonstrate the issue:

 

Dell XPS 15 9550 http://www.notebookcheck.net/Dell-XPS-1 ... 462.0.html
15.6 inch 16:9, 3840x2160 pixel, 10 fingers, SHARP LQ156D1JX01
Screen flickering / PWM not detected

Asus ZenBook Pro UX501VW http://www.notebookcheck.net/Asus-ZenBo ... 762.0.html
15.6 inch 16:9, 3840x2160 pixel, 10-point capacitive, IPS, ID: LGD04D4, Name: LP156UD1-SPB1
Screen flickering / PWM not detected

MSI WS60-6QJE316H11 Workstation http://www.notebookcheck.net/MSI-WS60-6 ... 105.0.html
15.6 inch 16:9, 3840x2160 pixel, SDC424B
The display backlight flickers at 1316 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 40 % and below.
The frequency of 1316 Hz is quite high, so most users sensitive to PWM should not notice any flickering.

HP EliteBook 745 G3 http://www.notebookcheck.net/HP-EliteBo ... 278.0.html
14 inch 16:9, 2560x1440 pixel, IPS panel
Screen flickering / PWM not detected

Gigabyte P34W v5 Xotic http://www.notebookcheck.net/Gigabyte-P ... 665.0.html
14.0 inch 16:9, 2560x1440 pixel, IPS, Name: LG Philips LP140QH1-SPB1
Screen flickering / PWM not detected

Schenker XMG U716 (Clevo P775DM1) http://www.notebookcheck.net/Schenker-X ... 740.0.html
17.3 inch 16:9, 3840x2160 pixel, AU B173ZAN01.0 (AUO109B), IPS
Screen flickering / PWM not detected

 

I selected higher than FHD display resolution models to compare with Lenovo ones in the previous post. As you can see, none of them exhibits that bad PWM implementation as Lenovo models do. Again, please diagnose the issue.

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 26,782
Message 3 of 49

Re: Low PWM frequency affects recent ThinkPad models

Lenovo ThinkPad P50s (3K)

http://www.notebookcheck.net/Lenovo-ThinkPad-P50s-20FKS00400-Notebook-Review.161463.0.html

 

The display backlight flickers at 219 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 90 % and below

 

Again, there must be something wrong with Lenovo BIOS/drivers that controls the display. No other vendor has such issues with almost all its production. Please focus on it.

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 26,431
Message 4 of 49

Re: Low PWM frequency affects recent ThinkPad models

X1 Carbon 2016 (WQHD)

http://www.notebookcheck.net/Lenovo-ThinkPad-X1-Carbon-2016-Core-i7-WQHD-Ultrabook-Review.162631.0.h...

 

The display backlight flickers at 220 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 90 % and below.

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 26,240
Message 5 of 49

Re: Low PWM frequency affects recent ThinkPad models

T460p (WQHD)

http://www.notebookcheck.net/Lenovo-ThinkPad-T460p-Core-i7-GeForce-940MX-Notebook-Review.163699.0.ht...

 

The display backlight flickers at 220 Hz (Likely utilizing PWM) 

 

All Lenovo 2016 models with better than FHD display resolution are having the issue. Still no response from Lenovo ?

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Czechnology
Fanfold Paper
Posts: 8
Registered: ‎09-21-2008
Location: CzechRep/Austria
Views: 25,827
Message 6 of 49

Re: Low PWM frequency affects recent ThinkPad models

Noone from Lenovo cares to comment on this issue? Smiley Sad

 

It seems that many users look for alternative manufacturers to not be affected by this problem.

Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 25,730
Message 7 of 49

Re: Low PWM frequency affects recent ThinkPad models

T460 (FHD)

http://www.notebookcheck.net/Lenovo-ThinkPad-T460-Core-i5-FHD-Notebook-Review.164879.0.html

 

Screen flickering / PWM not detected

 

It is still the same, FHD resolution displays does not have the issue while more expensive higher resolution ones does.

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 24,782
Message 8 of 49

Re: Low PWM frequency affects recent ThinkPad models

It is not a ThinkPad model but shows an extreme value that can really cause health issues. Such terrible display component should be banned by a FCC-like regulatory authority.

 

Lenovo Ideapad 500-15ISK

http://www.notebookcheck.net/Lenovo-Ideapad-500-15ISK-Notebook-Review.166579.0.html

 

The display backlight flickers at 50 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 90 % and below.

 

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Puppy
Bit Torrent
Posts: 1,822
Registered: ‎11-28-2007
Location: CZ
Views: 24,169
Message 9 of 49

Re: Low PWM frequency affects recent ThinkPad models

Lenovo ThinkPad T560 (Core i7, 940MX, 3K)

http://www.notebookcheck.net/Lenovo-ThinkPad-T560-Core-i7-940MX-3K-Notebook-Review.167770.0.html

 

The display backlight flickers at 220 Hz (Likely utilizing PWM) Flickering detected at a brightness setting of 90 % and below.

__________________________________
ThinkPad (1992 - 2012): R51, X31, X220, Tablet 8.
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Community SeniorMod
Community SeniorMod
Posts: 11,853
Registered: ‎06-06-2011
Location: RU
Views: 24,160
Message 10 of 49

Re: Low PWM frequency affects recent ThinkPad models

Hi, Puppy

Offtop here a bit, but the cause is similar.
Do you remember x220 reviews with results PWM related?

The other day I checked my 5+ years x220, with LCD panel IPS, the 1st gen, due to comparision with another devices. Flickering, started at very low value, becomes visible at 7/15 brightness level. But this brightness is unusable even in the dark environment. My regalar brightness is 11 of 15.

I.e.some reviewers mentioned PWM issue in the x220 w/out usage case, in theory. In one word, despite the mention of reviewers I don't take notice the flickering. May be devices in you scope of vision have the same features.

Finally, I don't remember flickering mentions in another devices I have - Yoga 260 (FHD LCD Chi Mei), x1c gen3 (WQHD LCD LGD), but there isn't such issue at any brightness level I notice.



x220 • Gobi 2000 3g | hdd, msata ssd, wwan, wifi, gps -- unique hand-made config
ThinkPad 25 Special Anniversary Edition. #retro. Signed by D.Hill
T470p | X1 Carbon Gen3 | Miix 2 10" | Yoga Tablet 2-1050F (Android) + BT Keyboard
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