Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Not my background, but it flickers in Fx5, Chrome 12 and IE8 on my Dell LCD.

Purple fade

If it does, can someone tell me why?

share|improve this question

migrated from graphicdesign.stackexchange.com Jul 28 '11 at 14:12

This question came from our site for Graphic Design professionals, students, and enthusiasts.

1  
It seems to be a hardware issue: either GPU or display. I found some similar problems through Google, albeit they're all dealing with grey gradients and laptops. Lagom LCD test page might help you to find settings that could fix the issue—or not. Yes, Super User might be the best place to fit. –  koiyu Jul 28 '11 at 9:31
    
which dell thing you are using?? –  Jack Jul 28 '11 at 10:40
1  
@koiyu this isn't actually a hardware issue at all - the monitor is working as designed. See my answer to this question if you're curious as to why. –  Breakthrough Jul 28 '11 at 15:10

2 Answers 2

up vote 5 down vote accepted

Flickering like this is a commonly known caveat with certain LCD panel designs. You can test which patterns may cause this here. This is a result of the constant voltage switching in the monitor's crystals, which attempt to create a somewhat uniform brightness in the picture you see (this is obviously done at a high frequency so you don't notice).

These voltages are alternated in "interleaving patterns", some of which may cause problems with certain images. Each manufacturer (and even their own sub-products) may use different LCD crystal masks and interleaving patterns, so this flickering effect is caused by different patterns for different monitors.

Since most LCD monitors refresh at around 60 Hz, a full duty cycle for the inversion takes two refresh cycles, causing the flickering at ~30 Hz - a quite noticeable flicker. For a more technical overview of why this occurs, see the Inversion section of this website.


Again, note that this is not a fault of your monitor, this is how all LCD monitors are designed. You can use the test I posted above to determine which pattern type causes this flickering, and avoid their uses if you are a graphics or web designer. Due to image compression when dealing with colour bands (like the question author posted), some colour dithering (which leads to colour banding) can also cause this flickering effect.

This interleaving problem can cause either pixel walk (it looks like the pixels are all moving in a certain direction rapidly) or flickering (flashing at a noticeable frequency) in the image.

share|improve this answer
    
Thanks.On my iMac there is no flickering at all. The Dell is a fairly new widescreen - I'll look up the model tomorrow –  mplungjan Jul 28 '11 at 16:08
    
@mplungjan Your iMac probably has an LED screen, not an LCD screen. All LCD screens in existence have this problem. If you don't want to see the pattern, you might have to purchase a newer LED screen, but regardless I would avoid the use of such patterns if you are a designer. –  Breakthrough Jul 28 '11 at 16:21
    
And LED screen is an LCD screen, is it not? It's just using a different light source. –  DA. Jul 28 '11 at 19:09
    
@DA sorry, yes you are correct. I thought that LED monitors varied the brightness by varying the back-lit LEDs, but this is not the case. This problem should occur on all monitors (albeit with different patterns). –  Breakthrough Jul 28 '11 at 19:39

I put this exact page on two monitors with different referesh rates - both driven by the same computer. On one you could see the refresh cycle, on the other it did not and was steady, both LCD screens.

I would try to alter the refresh rate (higher?) to see if that diminishes or eliminates the issue. OR Try to match the "optimal" for a particular monitor in color, resolution and refresh.

This seems similar to issues with old monitors and web-safe colors, dithering and the like but not the same thing.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.