Thinkpads Forum

Watching this youtube x301 review I see its display always flickering. Is this review showing a defect model?

http://www.youtube.com/watch?v=DHEP6zjeNpU

I'd say it's more of a camera/recording anomoly vs. a defective machine. I'd guess that the narrator is quite defective though .

But what kind of camera abnormality will only have the display of x301 flickering, while neither the background, the presenting person or the other monitor is flickering?

The screen of x301 seems to have some very old school refresh rate. It reminds me of analog connected 60 hz monitors which were always flickering in tv.

I own two X301 units and neither of the displays flicker.

If all X301 displays were flickering, you would be reading about it here.

Just because one display flickers on u-tube and the others do not is not any indication of the screen quality on the X301

Most of the images on u-tube are horrible

I can distinguish between TV / analog monitor / digital refresh rate (100% stable). I even gave a thinkpad back some years ago because of that. Hope that I can get a x301 one which would not present this experience on youtube for example.

The youtube video from thinkpads.com blog article Knife your Apple and get a ThinkPad once more shows a flickering x300 series display. Macbook Airs display is fine here.

I am probably one of the pickiest people on this forum. I've had two new X300's and I currently have two new X301's. I've had an incredible number of new ThinkPads personally, as well as the hundreds that I currently deploy in my company. Not one has a display flicker issue.

Anything is possible, especially with laptops that are abused and tossed about by the reviewers and journalists that don't have to pay for them.

Cheers...

That may be true. But I saw two videoreviews on youtube and they both show flickering. I'd be great to see one youtube review of the x301 without the flickering.

I believe that you are correct to say that the flickering you see on the X301 screen is indicative of the refresh rate. Any difference between it and the video camera's "shutter" speed used to record the clip will cause this illusion. Here's a write-up with some pictures:

http://codeidol.com/graphics/digital-vi ... t-Flicker/

edit: Further research seems to reveal it's not really the rate at which the pixels are displayed but the rate at which the CCFL is strobing.

I think you guys are mixing up two issues.

The flickering I see in those videos has as much to do with the camera settings, as rkawa points out, as it does with the screen. There are plenty of examples of x301s without that kind of flickering on YouTube: http://www.youtube.com/watch?v=M8cMo_gmbC4

Beyond that, there does seem to be a issue with some x301 screens, but looks to have little to do with refresh rate: http://www.youtube.com/watch?v=j8zprwn7 ... re=related or http://www.youtube.com/watch?v=ghcuklGFDp4

rkawakami wrote:I believe that you are correct to say that the flickering you see on the X301 screen is indicative of the refresh rate. Any difference between it and the video camera's "shutter" speed used to record the clip will cause this illusion.

That's exactly right. I know this to be true as I have a friend at a television station that called that to my attention many years ago, and I simply forgot to pass that on, during this discussion. There is simply no doubt about it, as it's obvious in many movie scenes over 100's of movies through the years, or live TV news broadcasts when they happen to show a clip in someones house where the TV is on. It's the same with the CRT computer screens and like you pointed out, a product of the CCFL backlight in TFT LCD displays.

Cheers...

High quality digital monitors do not flicker as they have a totally stable picture. Refresh rate regarding "on / off" flickering is some kind of analog thing. In fact, I noticed some years ago with a T20 the same low quality flickering issue.

ssd_thinkpad wrote:High quality digital monitors do not flicker as they have a totally stable picture.

Well, but current notebook lcd panels (especially the X300 one) are the lowest quality lcd panels ever. LCD panels might flicker but the technical reason is something completely different than low refresh rate known for CRT monitors. See links on that page http://www.techmind.org/lcd/ namely the "An application note from Intersil, concerning Vcom-originating LCD flicker".

The issue you are experiencing might be related to technology called "dithering". Super cheap LCD panels (read: horrible crap) used in all current notebooks including $3000+ ThinkPad models are trying to cheat your eyes/brain to pretend to display more than 262 000 colors by fast switching of two colors. Depending on the color conditions you might experience the flicker effect.

It is like single-chip DLP projectors and well-known rainbow-effect, some people can't stand the technology at all while some others barely notice the issue. So if someone says "the X301 display does not flicker" it means "s/he didn't recognize it". Solution ? None ... buy old ThinkPad with IPS panel

Puppy, thank you very much for your explanation! Now I understand why my eyes disliked that display that much that I gave the expensive notebook back the next day.

Mine doesn't "flicker" at all...

It's possible this "flicker" is caused by the pulse width modulation (PWM) of the led backlighting. Some users of Thinkpad x200 tablets and certain Apple Macs are complaining of severe eyestrain caused by too low a PWM frequency (around 90hz, in the case of the x200 tablet, according to one report). Apparently, even though the brain doesn't "see" the blinking, some sensitive eyes do, and the eye muscles trying to react causes the eyestrain. Brightness of LED-backlit screens is determined by how long the LED is lit each cycle. That means the problem is actually worse at lower brightness settings, where the pulse is more defined.

Is this pulse width modulation (PWM) true for every led backlight technology currently used for example in thinkpads?

The MacBook Air does not show my eyes this flickering, is it pulsing at a "better" frequency or is it not pulsing at all?

curious wrote:It's possible this "flicker" is caused by the pulse width modulation (PWM) of the led backlighting.

Good point. This is another aspect to be worried about when buying notebooks utilizing new "ultra-crappy" display technologies Lenovo has introduced. It is really sad that the top ThinkPad model is crippled by such subaverage components you would expect rather in $600 notebooks. Fortunately the backlight frequency can be measured and some magazines already do it in LCD monitors reviews. They should have started it for notebooks with buzzword-introduced LED backlight displays as well.

When byuing a new ThinkPad you have to worry about:
- will the display have any contrast ?
- will the display have acceptable polariser ?
- will the display have excessive backlight bleeding ?
- will the display have viewing angles above zero ?
- will the display have annoying dithering visible ?
- and now ... will the display have annoying backlight low frequency ?

Did you have to worry about such issues when buying a ThinkPad few years ago ?

No one mentioned the backlight so far. The way its brightness is lowered in particular. There are generally two ways of dimming the backlight, at least for CCFL lamps:
- lower the voltage driven to the lamp (analog),
- cycle the lamp power on/off very quickly (digital).

I'm not sure if this applies to LED backlited displays too but it should I guess.

Therefore the flickering in these videos may be caused by the digital dimming. A human eye won't see a difference between analog and digital but a video camera is a different story.

It surely has nothing to do with the image refresh rate which caused a similar looking flicker in CRT monitors.

yak wrote:I'm not sure if this applies to LED backlited displays too but it should I guess.

It applies to both CCFL/LED. In laptops/desktop monitors/tvs, PWM is used regardless of whether it is CCFL or LED.
You vary the duty cycle of the PWM signal, when you dim/brighten the display. A 50% duty cycle means that through one cycle, the "enclosed" area of the PWM signal, is proportional to the power. PWM is used mainly because it doesn't require any load resistors, which in a normal situation would have a voltage drop across them and thus dissipate heat. This and the fact that you can get programmable PWM generators in a small IC makes it easier to use - imagine the need to switch between resistors in a voltage divider, in order to dim/brighten the display light. Eww.

But a frequency of 90 Hz is just crazily low -especially for LED. One is supposed to choose the frequency not to be a multiple of any of the lcd refresh rate parameters - and not so low that people will notice the flicker. There is NO phosphor or "memory" in leds to smoothen out the flickering, like in CRTs or CCFLs for that matter - turning on an off the voltage (or reversing polarity) repeatedly on leds will be highly visible until maybe something like 500-800 Hz at least. Remember that the eye is much more sensitive to changes near the corners of the eye sight, so it might need to be even higher.

EDIT: I see that for the HV121WX6-100 LCD, the PWM frequency is allowed to be between 200 and 350 Hz.
If that's the usual frequency i'd hate to own an LED backlit panel.

ssd_thinkpad wrote:That may be true. But I saw two videoreviews on youtube and they both show flickering. I'd be great to see one youtube review of the x301 without the flickering.

Looking through this forum there are few complaints about flickering X301 displays. <personal attack removed by moderator>

Neither of my X301 displays flicker.

I tried Apple and they are a joke.

Troels wrote:But a frequency of 90 Hz is just crazily low -especially for LED. One is supposed to choose the frequency not to be a multiple of any of the lcd refresh rate parameters - and not so low that people will notice the flicker. There is NO phosphor or "memory" in leds to smoothen out the flickering, like in CRTs or CCFLs for that matter - turning on an off the voltage (or reversing polarity) repeatedly on leds will be highly visible until maybe something like 500-800 Hz at least. Remember that the eye is much more sensitive to changes near the corners of the eye sight, so it might need to be even higher.

EDIT: I see that for the HV121WX6-100 LCD, the PWM frequency is allowed to be between 200 and 350 Hz.
If that's the usual frequency i'd hate to own an LED backlit panel.

These screens were designed for a human eye. 200Hz may be indeed too low and cause an eye strain if used for a long time. The flickering however may still not be visible when you look at it directly. However, a digital camera works quite different and may cause the flicker to be visible, just like in this video. What do you think?

Troels wrote:It applies to both CCFL/LED. In laptops/desktop monitors/tvs, PWM is used regardless of whether it is CCFL or LED. <snip>

Thanks for your excellent post.

I stand corrected, as while I cannot see (nor can any of approx 30 of my employees that use the X301) and therefore we were convinced there was no flicker of consequence. However I can now understand why there are some people that can. And as you so aptly point out, especially if the frequency is as low as 200 / 350 Hz.

Cheers...

I must be one lucky guy as I ordered and received the 3rd X301 this week and we sat all of them side by side at our office and not one of us could detect a flicker. I thought maybe my old eyes could not tell but three of my employees are 19-23 years old.

The look on the face of the lucky employee when he got to his desk and found his new X301 on his desk!

Yeah, both LED and CCFL backlight lamps are dimmed using PWM. The difference is that (1) a CCFL lamp does not instantly stop emitting light the way an LED does, so the LED on/off makes for a more distinct flicker; and, more important, (2) CCFL tubes apparently have a PWM frequency in the khz, while LED's have a PWM frequency typically between 90hz and 500hz (one poster measured the x200 Tablet at 90hz; another measured two other laptops at 500 hz; I have measured a Toshiba A605-P10 at 200hz). If you Google the issue, you will find people reporting severe eyestrain for the x200 Tablet and some Macs.

Troels wrote:Remember that the eye is much more sensitive to changes near the corners of the eye sight, so it might need to be even higher.

That's why I always look away from displays to notice if it is flickering or not. If you find an old television, you can just take a look not directly on it but when in front of the tv, look whats behind it. Then you notice the flickering much better.

curious wrote:(1) a CCFL lamp does not instantly stop emitting light the way an LED does, so the LED on/off makes for a more distinct flicker; and, more important, (2) CCFL tubes apparently have a PWM frequency in the khz, while LED's have a PWM frequency typically between 90hz and 500hz

In this case the CCFL backlight seems to have its advantage despite users claim that there are no big differences in real battery life using either CCFL and LED ...

posting from my new x301 and while the display is certainly noticeably crappier than my dell 2408wfp, i do not see any flickering. while this screen is serviceable for now, i do wish they had offered a better lcd with this expensive laptop.

hofan41 wrote:posting from my new x301 and while the display is certainly noticeably crappier than my dell 2408wfp, i do not see any flickering. while this screen is serviceable for now, i do wish they had offered a better lcd with this expensive laptop.

Do you have an oscilloscope and photocell handy so that you can check the PWM frequency?

I wonder if Lenovo uses these cheap TN narrow-angle screens because they are more frugal powerwise? Otherwise, I agree it sucks.

curious wrote:I wonder if Lenovo uses these cheap TN narrow-angle screens because they are more frugal powerwise? Otherwise, I agree it sucks.

Cutting costs. People buy crap in general, why to bother with quality

Ok. I recently read the following article to understand the differences in quality between IPS vs. TN vs. PVA etc..

http://www.pureoverclock.com/article641.html

great article. Assuming the X301 is flickering because it has a TN screen, what IPS/PVA alternatives in the 13.3" screen form factor do we have? What company is using something other than a TN in a non-tablet laptop?

A 12" widescreen tablet is a nonstarter due to the decreased vertical height when compared to a 12" 4:3 screen.