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Slight screen flicker?

OP sdelcegno

6th December 2010, 07:39 PM   |  #1  
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I have a nook color, I was wondering if anyone notices a very slight screen flicker like a low refresh rate? Most people would not notice. It doesn't bother me much but I wanted to see if its normal. I notice it most on a dark grey background at 50 percent or lower brightness.

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6th December 2010, 08:37 PM   |  #2  
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Yes! finally someone that notices it! I have been posting this on other forums. I notice it too on dark backgrounds with about 20-40% brightness, Not sure if it can ever be fixed with an update, but it is sometimes annoying, although not highly noticeable.
6th December 2010, 09:43 PM   |  #3  
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I have worked with computer enough that I can tell the refresh rate of a crt just by looking at it. If its normal I am not to worried I justed wanted to know if it was defective because ill switch it out before I root it.

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7th December 2010, 06:56 AM   |  #4  
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I get the same thing, very noticeable when you are changing the brightness setting. I use the lowest brightness to read an eBook, and I can really notice the flicker when I lower the brightness, but I can notice it when I get back to the reading screen.
7th December 2010, 07:33 AM   |  #5  
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I see it on darker images...its so subtle I ignore it.

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7th December 2010, 03:44 PM   |  #6  
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I still have mine stock... but I see it as well.

Anyone that has loaded any other apps notice it in those apps? i.e. does it flicker noticably in Angry Birds? or other apps?

thanks.

J
7th December 2010, 03:59 PM   |  #7  
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I wonder if it being an IPS screen has anything to do with it. It doesnt bother me to much but causes more eye strain than reading from my htc g2. You would think they would make sure an ebook reader doesnt flicker. oh well i can deal with it.
7th December 2010, 04:32 PM   |  #8  
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Quote:
Originally Posted by sdelcegno

I wonder if it being an IPS screen has anything to do with it. It doesnt bother me to much but causes more eye strain than reading from my htc g2. You would think they would make sure an ebook reader doesnt flicker. oh well i can deal with it.

It's not the screen, per se, but the LED's that are lighting it up. From what I've read, LED's can't vary output with respect to voltage (they're not dimmable), so you have to pulse them very fast to change the output. I assume that the lower the "level" the more the LED is off vs. on, hence the flicker.

Dang I can't post links yet...

Go to Wikipedia, and look for :
/wiki/Backlight#Flicker_due_to_backlight_dimming

I'm pretty sensitive to this, but haven't noticed it on my iPad, but apparently it does it as well. I was wondering why the stock lowest brightness levels were so friggin' bright - probably at the threshold of flicker. You can dim more in a browser or ebook app, which is where I see reports of flicker.

Go to Discussions dot apple dot com
/thread.jspa?threadID=2398784

Another reason why I like my old CCFL IPS 12" ThinkPad X32!

-Dan
8th December 2010, 01:29 AM   |  #9  
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While you can dim an LED by limiting the current (either via inline resistors or with constant current drivers), you can only do so to a degree. Below a certain current, they will simply not light even though the current goes through the LED. On high performance LED's this is still at a pretty bright level. So instead you use PWM (Pulse Width Modulation) and vary the duty cycle to brighten and dim the LED. As the PWM is at a fixed frequency, with more or less of the cycle being lit or unlit, once the unlit portion becomes substantially longer than the Lit part, you can detect the "Flicker" if you are sensitive to it. This is usually particularly noticeable in the "corner of the eye" if you pan you vision across the area and the device gets paned across you field of vision.

This is done on all the new LED tail lights on cars as well and I hate seeing them at night, when they are almost making me nauseous from the flicker.
8th December 2010, 02:34 AM   |  #10  
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Good info thanks. Makes sense but wonder why I don't notice on my led backlit netbook. Guess every screen is different.

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