12-23-2011 11:31 AM
I have a problem with the new T420s screen. It causes eye strain and headache. I did some research and found that the LED PWM frequency is too low. Is there any way to increase the pwm frequency like in BIOS or graphics driver? I can not use it at all and I already missed the window to return the product. Or is there any better screen for replacement?
12-24-2011 06:53 AM
It's plugged in @ 60Hz. I can use my T61 for a whole day without any problem, but I can not read on T420s for half an hour. I heard that it's because of the LED backlight PWM frequency too low (90Hz?). I have also disabled Intel auto power saving. I do feel a little flickering when my eye moving fast on the screen. Macbook Pro does not have this problem although it also use LED backlight. I do suggest Lenovo come up with an solution with this.
Is there any way to increase the backlight frequency? A new LED invert card?
12-24-2011 09:54 AM
I've heard of other people having this kind of problem with LED monitors. There have been reports of end-users successfully modifying their backlights to prevent flickering, but they had to go through heroic measures to modify the circuit.
I don't notice any flickering on my T420s backlight (and I'm the kind of person who usually notices this kind of thing). In a case I know of where an end-user found the flickering of an LED monitor intolerable, it was the result of past brain damage which altered their visual perceptation.
I would probably try to return or sell the laptop. If you think fixing the backlight would solve your problem, I would see if you could get the LED into a maximum-brightness state all the time (hardwire it or switch brightness to maximum and disable dynamic contrast ratio) and then put a piece of dark material around the LED if it's too bright. The end results will probably be ugly and there's a good chance of damaging the laptop in the process.
12-24-2011 02:24 PM
Yes, if I put it full brightness, it seems fine for me except that it's too bright. Do you have the link of doing hardware modifications of the backlight? I will try it. Thanks.
12-25-2011 09:10 AM
12-28-2011 12:02 AM
You might want to calibrate your screen. I find that most screens ship too cool (blueish) from the factory and can be difficult to look at. The windows Magnifier will allow you to invert colors and that gives you white text on a black background.
01-01-2012 08:16 AM
01-01-2012 11:43 AM
sorry but only to return.
i tried the replacement thing myself - it's like talking to a wall. Lenovo is so convinient in thier spot like HP used to be so convinient - let's take a look and see where HP standing today.
the only company who keep make good laptops and not cut costs is Dell. i wish they would just do the software package the Lenovo did and i think lenovo would stay without any customers.