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esit
Paper Tape
Posts: 6
Registered: ‎01-24-2016
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Message 1 of 13

Does P50 FHD use PWM to control brightness?

Hi, I heard that the 4k display on P50 and P70 both use PWM for brightness. Is there any information about FHD on P50?

 

Thanks

Puppy
Bit Torrent
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Location: CZ
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Message 2 of 13

Re: Does P50 FHD use PWM to control brightness?

To make it clear, all displays use some kind of PWM to control brightness, it is almost impossible to do it without using it (HP DreamColor might be the exception, still not sure), especially in laptops. The big difference is how the PWM is implemented, what frequency and modulation it uses. So the "PWM-free" so called displays are rather an "annoying-free PWM implementation" displays. It is not a rocket science, just the level of cutting costs applied, as usually these days. How comes that a cheaper model can get better quality display than an expensive one ? Because no one cares. It is just "component" having size and pixel resolution.

 

Unfortunately you have to wait for deep detailed reviews like notebookcheck site do because the price tag does not guarantee any quality anymore Smiley Frustrated Even worse scenario, if there are multiple vendors of the "same" display for particular model (T440 LG vs AUO etc.) you are completely out of luck. Frustrating, eh ?

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esit
Paper Tape
Posts: 6
Registered: ‎01-24-2016
Location: US
Views: 4,944
Message 3 of 13

Re: Does P50 FHD use PWM to control brightness?

thanks for those information.

 

i read a notebookcheck review on E560, which is said to be PWM-free.

I also read from lenovo's lists of frus, where i noticed that P50 and E560 could use the same FRU for FHD non-touch display.

 

However, i am not able to tell if that PWM-free diaply on E560 is the common FRU between E560 and P50.

 

The PWM-free FHD on E560 is LP156WF6-SPK2

The common FRU for FHD non-touch is 00HT919. Its description is "15.6,FHD,AG,N-Touch,IPS,SDC,slim"

Is there a way to tell if "LP156WF6-SPK2" is "15.6,FHD,AG,N-Touch,IPS,SDC,slim" ?

Puppy
Bit Torrent
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Message 4 of 13

Re: Does P50 FHD use PWM to control brightness?


@esit wrote:

However, i am not able to tell if that PWM-free diaply on E560 is the common FRU between E560 and P50.


It is hard to confirm as long as there is no P50 review yet. I wouldn't be surprised if the cheaper E560 actually gets better display than P50. It is just lottery, unfortunately. No one (read Lenovo) cares. Otherwise they wouldn't have used such low-PWM-on-all-brightness display in $7000 flagship P70 workstation.

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Puppy
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Message 5 of 13

Re: Does P50 FHD use PWM to control brightness?

P50 FHD review http://www.notebookcheck.net/Lenovo-ThinkPad-P50-Workstation-Review.158713.0.html

 

  • Screen flickering / PWM not detected

Good display for E560 but given a $2500+ workstation I would expect better one. Actually the one in E560 is slightly better Smiley Indifferent

 

Model

E560

P50

Panel

LP156WF6-SPK2

LP156WF6-SPK1

Contrast ratio

952:1

774:1

Average luminance

234 cd/m²

236 cd/m²

Brightness Distribution

83 %

78 %

AdobeRGB coverage

36.6 %

37 %

sRGB coverage

57.3%

58 %

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Puppy
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Message 6 of 13

Re: Does P50 FHD use PWM to control brightness?

Be careful, Lenovo has started the screen lottery again Smiley Mad

 

https://download.lenovo.com/parts/ThinkPad/p50_frubom_20151130.pdf

 

00HT919 N 15.6,FHD,AG,N-Touch,IPS,SDC,slim
00HT920 N 15.6,FHD,AG,N-Touch,IPS,BOE,slim
00HT921 N 15.6,FHD,AG,N-Touch,IPS,LGD,slim

 

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esit
Paper Tape
Posts: 6
Registered: ‎01-24-2016
Location: US
Views: 4,670
Message 7 of 13

Re: Does P50 FHD use PWM to control brightness?

so, the display on P50 is a lottery, and i lost: mine has PWM flickering.

 

i can see strips with my phone's camer when the brightness level in windows 10 is below 50%.

 

 

 

i also did a short test:

 

this picture is taken at the 3rd lowest brigtness setting in windows 10

(~30% in windows scale. not necessarily the actually percentage to max brightness)

 

i count 6 images of my finger moving across the display, which should imply that 6 to 7 cycles in this picture. its explosure time from EXIF is 1/30 sec.

Puppy
Bit Torrent
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Message 8 of 13

Re: Does P50 FHD use PWM to control brightness?

Do you know the exact panel FRU ?

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mPiotr
Punch Card
Posts: 7
Registered: ‎05-30-2016
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Message 9 of 13

Re: Does P50 FHD use PWM to control brightness?

Is it possible to determine the exact LCD panel model before buying if you have notebook serial number ?

 

Is hardware monitor id "LEN40BA" always equivalent to LG LP156WF6-SPK1 ?

Puppy
Bit Torrent
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Message 10 of 13

Re: Does P50 FHD use PWM to control brightness?


@mPiotr wrote:

Is it possible to determine the exact LCD panel model before buying if you have notebook serial number ?


No. You are still not a valuable customer for Lenovo giving $4000 for laptop so Lenovo won't guarantee you get what you have paid for.

 

I think that any panel using lower than 1000 Hz PWM frequency should be considered as harmful to health and banned by regulatory authority. It is similar issue to radiation known for CRT monitors.

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