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Thread: BEWARE laptops/tablets/monitors that use PWM to dim the screen!!

  1. #1
    Join Date
    Feb 2014

    Default BEWARE laptops/tablets/monitors that use PWM to dim the screen!!

    I own two tablets from a certain company. The newer gen one hurts my eyes when I look at the screen. I put them both at the same brightness of 25%. One hurts my eyes, while the other doesn't. I was perplexed as to why until I discovered that to cut costs, some displays will use PWM (Pulse-Width Modulation) to dim the screen.

    Basically, if you boycott all products with PWM, the manufacturer will likely never use the component again...

    Anyways, it seems there are two ways to decrease the brightness of an LCD display:

    1. The analog method: Basically, this actually decreases the illumination of the LED backlight. But it costs a little more than the method below.

    2. The PWM (Pulse-Width Modulation) method: This is basically cheating just to save the manufacturer a few pennies. In PWM, say you set the display at 50% brightness, what really happens is the LED will be bright at 100% for half the time, then off for the other half. Imagine staring at a full brightness screen every other millisec. It's nuts! Not only will this damage the eyes, but the cycling on and off will cause cilliary muscle spam.

    How to test an LCD screen for the presence of PWM dimming:

    Simply wave a pen or your hand over a white screen at 25% brightness and look at the motion blur generated. If the blur looks smooth and continuous, the display uses analog dimming. But if the blur looks like segmented multiple repeating patterns, then it is a corner-cutting display with PWM dimming.

    What you can do to combat PWM: Apply 5% VLT tint over the display (these will only cost a few bucks on eBay), set the brightness to 100%.
    Last edited by hirobo2; 02-14-18 at 11:54 AM.

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